the process. In order to determine the source of this heat, he constructed a metal cylinder weighing about a hundredweight, which was caused to rotate against a blunt steel borer. After the lapse of half an hour the temperature of the cylinder was found to have increased from 60° to 130°, while the particles of metal worn off only weighed 837 grains. It was evident, then, that the heat which had elevated the temperature of the heavy cylinder 70° could not have been evolved by a change of capacity for heat in this small quantity of metal.

In another experiment the cylinder was immersed in a vessel containing about two and a-half gallons of water, and made to rotate against the blunt borer as before, and in the course of two hours and a half the water was caused to boil by the heat thus evolved. The supply of heat thus obtainable appeared, indeed, to be inexhaustible. The power which drove the cylinder was in this case converted into heat, just as when the brake is applied to a train the wheels are seen to smoke and give off sparks, owing to the motion of the train being converted into heat, and thereby destroyed. We see now the reason why grease is applied to the axles of wheels and to pieces of machinery; if it be absent the friction is increased, and then a portion of the power is wasted by being converted into heat, instead of being employed to do the work of the machine.

In these experiments the quantity of heat produced has been so great as at once to be observed: very often, however, the amount is so small that it cannot be well shown, even by an ordinary thermometer. The mode, therefore, usually adopted in rendering its presence manifest is to use a thermo-electric pile.

If a bar of bismuth and one of antimony be joined end to end, and the point of junction heated, a faint current will pass between the ends of the bar, and will deflect the needle of a galvanometer. When several such compound bars are employed, much greater sensitiveness is obtained. The bars are bent in the middle, so that the alternate junctions may be at one side of the pile, as seen in Fig. 2. The ends are then connected, by the binding screws seen on the top in Fig. 1, with a delicate galvanometer, and we have thus a means of rendering visible the faintest amount of heat. So delicate, indeed, may this instrument be made that the warmth of the hand, when held at a distance of several feet, will visibly deflect the needle. An instrument of this kind is of great service in all researches on heat; it is, in fact, almost indispensable, and hence frequent reference will be made to it in these lessons.

The next sources of heat which we must refer to are percussion and compression. An illustration of the production of heat by the former has already been given in the experiment of letting fall a leaden ball. A piece of soft iron, too, may be rendered red-hot by a few skilful blows on an anvil; and a blow or two with a hammer on an ordinary nail will at once raise its temperature sufficiently to affect the thermo-electric pile, and often to ignite a lucifer.

The best means of exhibiting the effects of compression is by the compression syringe represented in Fig. 3. A piece of stout glass or metal tube closed at one end, and having an internal diameter of about half an inch and a uniform bore, has a piston fitted tightly to it: in the under side of this piston is a small cavity in which a small fragment of tinder is placed. The tube is now placed against a wall or some support, and the piston quickly forced into it. So much heat is produced by the sudden compression of the air that the tinder is ignited, and when hastily drawn out will be found red-hot and smouldering.

When a jet of hydrogen gas is allowed to strike upon very finely divided platinum it sometimes renders it red-hot, and thus the gas becomes ignited. This may partly be attributed to condensation of the gas in the pores of the platinum, and partly also to chemical action.

This property of spongy platinum is sometimes turned to account in Dobereiner's lamp, which is shown in Fig. 4. It consists of two glass vessels, A and B, the neck of A reaching to the bottom of B. A piece of zinc (z) is placed in the lower one, and diluted sulphuric acid is poured over it; the upper one is then fixed tightly in its place, the neck being ground so that it may fit air-tight. The action of the acid on the zinc gives off hydrogen, which drives the liquid into the upper vessel, and thus leaves the zinc dry. As soon as the tap in the tube H is turned the gas escapes, and coming into contact with the spongy platinum contained in D, is ignited. The acid then passes again into B, and a fresh supply of gas is generated.

The next and perhaps the most important source of heat is chemical action. Nearly all chemical combinations are attended with the production of a greater or less degree of heat. If we take some sulphuric acid, and pour it into a vessel containing water, the heat thus evolved will at once be seen. When the act of combination goes on very rapidly, light is often produced as well as heat, and the term combustion is then commonly applied to the change. In reality, however, it is as much combustion when a piece of iron slowly rusts in the air as when iron wire is burnt in oxygen gas; and further, the same amount of heat is evolved during the whole process, whether the combination take a shorter or a longer time.

If a quantity of tan or other dry vegetable matter be consumed in a fire, a large amount of heat is given off, but it is very soon over; if, on the other hand, this matter be allowed to decay so as to form a hot-bed, a much less degree of heat will be produced, but it will continue for a much longer period, and on the whole the same total quantity will be produced as in the former case.

In calculations of this kind it is necessary to have some unit to express the quantity of heat produced, for the thermometer merely reveals to us its intensity. The unit, accordingly, which has been selected as being simple and convenient is the quantity of heat required to raise 1 pound of water 1° in the Centigrade scale, that is, 1° Fahrenheit. This amount, however, is not absolutely uniform in all parts of the scale, and the interval between 0° Cent. and 1° Cent. is therefore usually fixed upon. As a result of many experiments, tables have been compiled which show the number of these thermic units which would be produced by the combustion of 1 pound by weight of different substances. The following are a few of these numbers :

Hydrogen. 34,000 Coke
Oil of turpentine 10,080 Coal
Olive oil

. 7,000
. 8,000

Alcohol . 7,180 Phosphorus. 5,900 . 9,860 Tallow 8,000 Wood (dry). 4,000 Though these numbers represent the amount of heat actually produced by combustion, it is but rarely that we can obtain and use anything like this amount, a large portion being always wasted. In the steam-engine, for instance, the work accomplished by any amount of fuel is seldom more than of the theoretical amount, and often falls far short even of this. A large amount is given off with the smoke in the chimney, and much is lost by being communicated to the machinery and given off by radiation.

In an ordinary fireplace, too, only a small fraction of the heat generated is serviceable in warming the room, the greater portion ascending the chimney, and being occupied in producing the upward draught. On this account many other modes of warming are more economical. The open fire, however, remains, and probably will remain, the most popular on account of its pleasant and comfortable appearance.

In most cases the substance consumed combines with the oxygen of the air. Heat, however, is produced by other combinations, as, for example, by that of hydrogen with chlorine. If a little sulphuric acid be dropped upon a mixture of pow dered sugar and chlorate of potash, the chemical action will be so intense that sufficient heat will be generated to inflame the mixture: this mode of producing heat is sometimes employed. The ordinary lucifer match is tipped at the end with a compound which is decomposed at a very low temperature. The friction of the match against the box is sufficient to raise it to this degree, and then the compound inflames and ignites the wood.

Vital action is another source of heat, the temperature of the human body being above that of the surrounding air. This may, however, be regarded as a result of combustion, for a portion of the food taken into the system is really consumed, that is, its carbon unites with the oxygen of the air, and by this slow combination heat is produced which maintains the temperature of the body.

The only other source of heat which we shall refer to now is electricity. We have seen already how in the thermo-electric pile heat is converted into electricity, and we shall find more fully in our Lessons on Electricity how it may in turn be converted into heat. A simple illustration of this is seen if a piece of thin platinum wire be taken and made to form part of the circuit round which a powerful electric current is passing; the wire will very shortly become white-hot, and even be fused. It is in this way that cannon and torpedoes are fired by the

agency of an electric current.

dol'ro into dorrò (from dolere), ven'ro into verrò (from venire). Irregular verbs, the infinitive mood of which is contracted, derive their future tense and present conditional either exclusively from the contracted, or from the contracted as well as from the original form of their infinitive.

These are, I believe, the principal irregularities to which, in their future tenses and present conditionals, all the Italian verbs are liable. I consider such generalising explanations as useful, and a frequent reference to them will enable even a short memory to retain the numerous varieties of the Italian verbs. 14. See remarks on the conditional present of essere. 15. The difference between the first person of the plural of the conditional present and the same person of the future is a double m. The forms amaressimo or amerissimo for ameremmo, and sentiressimo for sentiremmo, are erroneous.

16. The second person plural of the conditional present changes the syllable rete of the future into reste.

17. The third person plural of the conditional present adds ro to the termination ebbe of the singular. The termination ebbono is milder than ebbero. The termination iano is formed by adding no to the termination ia of the singular, and is especially in use in poetry and in grave or solemn prose. Instead of iano, especially in poetry, also the termination ié-no or iên is in use (by changing a of the penultima into e, and transferring the accent from i to e), as, a-ma-riê-no, te-me-riê-no, sen-ti-riê-no, for ameriano, temeriano, and sentiriano.

III. REMARKS ON THE IMPERATIVE MOOD.

1. See remarks on the imperative mood of essere. In the first conjugation the second person singular of this mood is identical with the third person singular of the present tense, indicative mood, and in the other conjugations with the second person singular of the same tense, thus:

Tá-li co-se non ván-no fát-te co-sì, such things are not done in this way.

Tút-ti ri-má-se-ro ma-ra-vi-gliá-ti, all were astonished.

There is a peculiar way of expressing the passive voice by means of the pronoun si, the use of which will be explained in the additional observations on the regular verbs.

To change active verbs into passive the case-sign da or the preposition per must be put before the subjects of the active voice on which some act depends, or which are its authors or causes: for example, the following sentences

Sci-pió-ne di-strús-se Car-tá-gi-ne, Scipio destroyed Carthage; An-ní-ba-le scon-fís-se più vôl-te i Ro-má-ni, Hannibal several times defeated the Romans;

In-tro-dúr-re al-cú-no, to introduce somebody,

when changed into the passive will run as follows:

Car-tá-gi-ne fu di-strút-ta da Sci-pió-ne, Carthage was destroyed by Scipio.

I Ro-má-ni fú-ron più vôl-te scon-fit-ti da An-ní-ba-le, the Romans were several times defeated by Hannibal.

Es-se-re in-tro-dot-to da al-cú-no, or per al-cú-no, to be introduced by somebody.

The following paradigm of the conjugation of the passive verb essere amato, to be loved, may serve as a model for the conju gation of passive verbs.

I. INFINITIVE MOOD.

Present.

Essere amato, to be loved.

Perfect.

Essere stato amato, to have been loved.

Present Gerund.

Essendo (io) amato, being loved (i.e., because, etc., I, etc., am loved).
Essendo (noi) amati, being loved (i.e., because, etc., we, etc., are loved).

Past Gerund.

Essendo (io) stato amato, having been loved (i.e., because, etc., I have been loved.

Essendo (noi) stati amati, having been loved (i.e., because, etc., we, etc, have been loved.

Past Participle.1
Stato amato, having been loved.

The Italian language, like the English, has no special terminations to express the passive voice, which is formed, as in English, by means of the auxiliary verb essere, to be. It is on this account sufficient to know this verb and the past participle of the principal verb, since the combination of these two through all tenses forms the passive voice, as, amo, I love; sono amato, I am loved; temo, I fear; sono temuto, I am feared; and thus through all the tenses of essere. The verb ve-ní-re, to come, may also be used instead of essere, with a passive verb, but only Sing. Sono or vengo am-ato, I am Sing. Era stato am-ato, etc., I hed

loved.

Present.

II. INDICATIVE MOOD.

Sei or viêni am-ato.

E or viêni am-ato.

Siete or veníte am-ati.
Sono or vengono am-ati.

Imperfect.

loved.

in its simple, and never in its compound tenses, as, vên-go
a-má-to, I am loved, instead of sono amato; but it is not allow-
able to say só-no ve-nú-to a-má-to, instead of sono stato amato, Plu. Siamo or veniamo am-ati.
I have been loved, etc. In addition to venire, occasionally
the verbs re-sta-re (to remain, be left), ri-ma-né-re (to remain),
an-da-re (to go), and stá-re (to stand), may be employed as
auxiliaries to conjugate the simple tenses of the passive voice.
They express, like venire, the continuance of some act or state Sing. Era or veníva am-ato, I was
of a person or thing with greater energy and elegance than
essere. For this very reason they must be used sparingly. That
the use of essere and venire is not arbitrary-essere denoting
that some act has been accomplished, while venire generally
expresses that some act has commenced without being com-
pleted--may be seen in these two phrases: il quá-dro è di-pín-to,
the picture is painted, and il quá-dro viê-ne di-pin-to, the picture
is being painted. Other phrases illustrating the use of these Sing. Fui or venni am-ato, I was
verbs in the passive voice, are-

Viên lo-dá-to da tút ti, he is praised by all.
Vên-ne ac-cu-sá-ta, she was accused.
Ver-rán-no bia-si-má-te, they will be blamed.

Qué-sta vô-ce va pó sta prí-ma, this word is (i.e., must be) put first.
E-gli sta se-dú-to, he is seated (i.e., he sits).

The past participle, forming with the tenses and moods of essere the passive voice, must be considered as a real adjective agreeing with the passive subject or nominative in gender and number. This rule is invariable, even when the verbs andare, restare, rimanere, stare, and venire are used in the place of essere: for example:

Nói (nô-mi-ni) siá-mo stá-ti in-gan-ná-ti, we (men) have been deceived.
Nói (don-ne) siá-mo stá-te in-gan-ná-te, we (women) have been deceived.

Indeterminate Pluperfect.

been loved. Determinate Pluperfect. Sing. Fui stato am-ato, etc., I had

been loved.
Future.

Sing. Sarò or verrò am-ato, I shall
be loved.

Sarai or verrái am-ato.
Sarà or verrà am-ato.

Plu, Saremo or verrémo am-ati.
Sarete or verréte am-ati.
Saranno or verránno am-ati.
Future Perfect.
Sing. Sarò stato am-ato, etc., I shall
have been loved.
Conditional Present.
Sing. Sarei or verréi am-ato, I sha'!
be loved.

Saresti or verrésti am-ato.
Sarebbe or verrebbe am-ato.
Plu. Saremmo or verrémmo amati
Sareste or verréste am-ati.
Sarebbero or verrebberoam-ati

Conditional Past. Sing. Sarei stato am-ato, etc., should have been loved.

Present.

IV. SUBJUNCTIVE MOOD.

Imperfect.

mirrors, and refraction through lenses, the incident pencils being direct. They must also be able to discuss the solar spec

Sing. Sia or vênga am-ato, I may be Sing. Fossi or venissi am-ato, I trum, and to explain the construction and principle of action of

Sii or sia venga am-ato. [loved.

Sia or venga am-ato.

Fis. Siamo or yeniámo am-ati.

Siate or veniáte am-ati.

Siano or vengano am-ati.
Perfect.

Siag. Sia stato am-ato, etc., I may
have been loved.

Plu. Siamo stati am-ati, etc.

might be loved.

Fossi or veníssi am-ato.

the eye, simple optical instruments, the camera obscure, and reflecting and refracting telescopes. In Physical Optics, the fundamental hypotheses of the undulatory theory respecting the Plu. Fossimo or veníssimo am-ati. origin and propagation of light must be acquired; and the

Fossi or venísse am-ato.

Fosti or veníste am-ati.

Fossero or venissero am-ati.

Pluperfect.

student must be able to give a general explanation of interferences, the formation of Newton's rings, and descriptions of simple experiments which elucidate the effects of interference. Sing. Fossi stato am-ato, etc., I The phenomena of what is termed polarised light must also be might have been loved. studied, and the description of simple experimental modes of producing them.

I. REMARKS ON THE INFINITIVE MOOD.

The subject of Astronomy will, in its mathematical treatment, 1. The Italian language has no present and future participles involve some acquaintance with the elements of spherical trigoin the passive voice. Such words as ve-ne-rán-do, venerable, tonometry, and for this purpose the circles of the sphere, measures be revered; re-ve-rên-do, reverend, venerable, and similar ones, of the sides and angles of spherical triangles, and the supplewhich, in imitation of the Latin language, might be called future mental triangle, should be carefully read. The student cannot participles of the passive voice, must be considered as adjec-be too familiar with the systems of great circles to which the tives. The learner must have observed that there is also no positions of the heavenly bodies are referred the ecliptic, the future participle in the active voice. Only a few words which equinoctial, and the celestial horizon. He should also be able might be thought to be such are, as it were, remains of the to describe and explain the principal phenomena depending on Latin language, and must be considered as adjectives pointing the motion of the earth round the sun, and its rotatory motion to something to come; as fu-tú-ro, future; ven-tú-ro, future, round its own axis; to write a general description of the solar next, to come; re-di-tú-ro, that is to return. system; and to give a general explanation of solar and lunar eclipses.

THE UNIVERSITIES.-XV.

LONDON.-IV.

We now close our series of papers on the principal Universities of Great Britain and Ireland by a supplementary paper on the University of London, respecting

THE SECOND B.A. AND M.A. EXAMINATIONS.

The second examination required to be passed by candidates for the degree of Bachelor of Arts is held annually, commencing on the fourth Monday in October. Candidates who are not graduates in science must have passed the first B.A. examination at least one academical year previously, and must transmit to the Registrar, one calendar month before the commencement of his examination, a satisfactory certificate of good conduct, which should be signed by two gentlemen of position.

The fee for this examination is £5, which must be paid on the candidate's signing the register, at a time of which be will be informed by the Registrar. The examination is conducted by means of printed papers, the examiners seldom exercising the right which is reserved to them of putting vivá voce questions.

This branch of the examination is an extended and difficult one. Great attention should be paid to its preparation, and facility acquired in the solution of problems. At the last examination no less than 49 out of 141 candidates failed to

satisfy the examiners in mechanical and natural philosophy, a proportion which fully justifies our advice.

The extent of acquirement in Animal Physiology, the second subject of examination, is, the calendar states, such as may be obtained by the thorough mastery of any elementary treatise; as, for instance, the explanatory series of lessons on Comparative Anatomy, Animal Physiology, and Human Physiology in the POPULAR EDUCATOR, which furnish all necessary information on these subjects. Attention must not be devoted solely to human physiology; since the questions in comparative physiology are always equally, and frequently more, numerous; and the number of those relating to the comparative structure of the digestive, circulatory, nervous, and respiratory organs, and the organs of special sense, in man and the lower animals, is generally a feature in the examination papers. The subdivisions of the subject to which attention should be chiefly directed are-the mechanical, chemical, and vital properties of the several elementary tissues of animals; the nature and composition of the principal substances used as food by animals; the comparative structure and action of the organs of digestion, absorption, and assimilation; the composition of the chyle, lymph, and blood; the comparative structure, arrangement, and actions of the circulatory and respiratory organs in the animal series; the tory organs, and the principal varieties presented in the structure of the liver and the kidney; the objects of the several excretory processes; the development of heat, light, and electricity by animals; the comparative structure and actions of the nervous system and of the organs of sense; animal mechanics; and the general history of development and metamorphosis in the principal types of animals.

The first subject of examination is Mechanical and Natural Philosophy, in which two papers are set, each occupying three hours. The subject includes (a) Statics; (8) Dynamics; (7) Hydrostatics, Hydraulics, and Pneumatics; (8) Optics (Geo-chemical effects of respiration; the essential structure of secremetrical); (e) Acoustics; (C) Optics (Physical); (7) Astronomy; the whole treated experimentally, and also mathematically, so far as the subjects of the first B.A. examination are applicable

to them.

In Statics, candidates must be familiar with the definitions and axioms of the science, the composition and resolution of forces, the mechanical powers, the centre of gravity, and simple cases of equilibrium of bodies or systems of bodies under the action of gravity; and able to solve problems involving a knowledge of these subjects. In Dynamics, it will be necessary to master the laws of motion, and propositions required for determining the rectilinear motion of a body, whether free or along inclined planes; the motion of projectiles; and the simpler cases of motion round centres of force. The examination in Hydrostatics, Hydraulics, and Pneumatics involves a knowledge of the elementary propositions respecting the nature, transmission, and intensity of fluid pressure; the conditions of equilibrium of floating bodies; the nature and simple properties of elastic fluids, and the pressures produced by them; specific gravity, and modes of determining it; the common and forcing pumps; the hydrostatic press; the barometer; the air-pump; and the steam-engine.

In Geometrical Optics, candidates must know the laws of reflection and refraction; reflection at plane and spherical

We recommend candidates to prepare very carefully this portion of the examination, which at the last examination was only surpassed in fatality by mechanical and natural philosophy, and which will, to the majority, be a new but most interesting branch of study; and to comply, if possible, with the stronglyexpressed recommendation of the University authorities, either to attend a short course of lectures in which the structure of the principal organs of the animal body is demonstrated, or to obtain information through the private aid of some person conversant with the subject, and to gain some practical knowledge by performing a few rough dissections either of the human subject or of the chief organs of the higher mammalia. The student will also find it desirable to construct analytical tables of the composition of blood, chyle, lymph, urine, one, etc., and the other chief constituents of the human body.

The classical branch of this examination consists of one Greek

and one Latin prose subject, selected two years previously by

which questions are almost invariably set, and from Sir William by subtracting the index of the divisor from that of the dividend.