always adheres to polished surfaces, frequently prevents contact between the metal and the acid.

"In the batteries described the effects produced, have resulted from the decomposition of water. Prof. Grove has, however, constructed a gas battery, in which the combination of oxygen with hydrogen, and the consequent production of water is sufficient to afford a current of electricity.

"LUMINOUS EFFECTS.

The application of the electric light to lighthouse purposes, has been highly successful; and for many months, the South Foreland shone brilliantly with the light produced by the magneto-electric machine, which we shall describe under the head of Electro-Magnetism. At the present time, some parts of Paris are thus lit, and the effect is said to be very fine. The electric light seems to have what we may call a spacepenetrating power, and it can accordingly be seen further in a fog than any other kind of artificial light; its value for lighthouses, on this ground alone, is therefore very great. The color of the electric light varies according to the materials used as points, between which the arc of flame is produced.

"CALORIFIC EFFECTS.

"It will be observed, that the thick wires which convey the electricity from the battery are not easily heated, except at the points, after they have been in contact. This is because they are sufficiently large to carry the current without affording any considerable resistance to its passage. If, however, these wires are joined together by means of a thin iron wire which is too small to carry the current, and which accordingly affords great resistance to its passage, then a large amount of heat will be set free, and the wire will either be greatly heated, or if the battery be very powerful, the heat will be sufficient to melt even a platina wire. The length of wire heated by any battery depends on the number of cells; whilst the thickness of the wire which may be melted, depends on the size of the plates.

"Different metallic wires, of the same thickness, vary in their power of carrying a voltaic current. Copper, as the best conductor, is the most difficult to melt; and iron or platina, which

are much inferior in their conducting power, are very readily heated by the voltaic current, and hence are most suitable for illustrating these effects.

"The relative conducting power of wires of different metals, or of different thicknesses, may be conveniently illustrated by making a chain of them. Thus, a chain of silver or copper wire, with links of iron wire, will, when made to form part of the conducting course of a powerful battery, present the appearance of an alternation of cold and red-hot wires. Or the thick wires may be nailed to the edge of a table, and each joined by means of finer wire, when the latter, on conveying the current, will be instantly melted.

"The electricity of a powerful battery may be conveyed to any distance by means of properly insulated wires; and for this purpose, gutta-percha answers admirably. The heating powers of the voltaic battery have thus been applied for blasting, military, engineering, and numerous other purposes.

"A cartridge, closed at one end, and well pitched over, to render it water-tight, is to be filled with gunpowder, and into it may be fitted a cork, through which two thick copper wires have been passed, their inner ends being joined together by a fine iron or platina wire. The iron thus rests in contact with the powder. The conducting wires are attached to the coarse wires of the cork, and their other ends are laid near the battery. The cartridge is then to be sunk into a pail of water, or a pond, and one of the wires may be connected with one end of the battery. On the other wire being brought into contact with the battery, the current at once passes; the fine wire in the gunpowder becomes ignited, and an explosion at once ensues.

"A very ingenious application of voltaic electricity has been made by Mr. Hart, an optician, and philosophical instrumentmaker, of Edinburg, for the purpose of lighting chandeliers, and other gas arrangements which are inaccessible by ladders. He arranges over each burner two main conducting wires, connected by means of a fine platina wire. On the ignition of the latter by the voltaic battery, the gas is simultaneously lit in each burner; and by means of an electro-magnet, the platina wire is instantly removed from the flame when the latter is produced. This, of

course, prevents the destruction of the platina by the impurities. which coal gas always contains. The experiment may be easily repeated by means of a single gas-burner: indeed, a tallow candle may be readily ignited by a wire heated white-hot by means of the voltaic battery.

NOTES.

THE AMERICAN Academy of Dental Science, Boston, desires to present, at the coming centennial, in Philadelphia, the progress made in Dental Science during the last one hundred years. All persons having interesting facts to communicate are invited to send them to the Secretary of the Committee, Dr. Geo. T. Moffatt, Boston, Mass.; and it should be done as soon as possible.

A large number of Dentists have asked for, and received by mail from the Editor, one dozen of dental test tubes, free of charge, since the January number was issued. There is experimental work going on which will benefit the profession and the public. Send, if you wish them.

In the April number of this journal will appear an article on Cylinder Fillings, by one of the most eminent Dentists of the West.

MISSOURI DENTAL COLLEGE, Friday, March 10th, 1876—The degree of Doctor of Dental Surgery was conferred on Drs. J. Ward Hall, Alfred R. Reed, Charles C. Buckner and P. B. Mathiason.

Many persons ask, "who is Gold Foil ?" I shan't tell, "but it ain't me."

Dr. W. F. Southern died at Memphis, Sunday, March 12th. The celluloid plate users are happy now that their long fast is

over.

Analyses of air, by PASTEUR, have demonstrated that the germs of bacteria, and other living forms, are everywhere present.

Dr. Eberth, of Zurich, has found bacteria in the perspiration. They have been found in the brain of man soon after death.

The electric force required to decompose one grain of water is equal to 800,000 discharges of a Leyden jar.

Breathing through the nose is a much more healthy mode of respiration than through the mouth. Plenty of reasons; think of them yourself; and when operating on the mouth of a patient, the only admissable way.

Ulcerating temporary teeth sometimes cause inflammation and death of the permanent half formed teeth beneath them.

BOOK NOTICES.

Home and School, published by John P. Morton, Louisville, Ky. I consider it a kindness to the readers of the MISSOURI DENTAL JOURNAL to draw their attention to the "Home and School." It is finely illustrated; good paper, good type, and all for a $1.50 for 600 pages.

Another journal which I wish could be more extensively taken, although its circulation is very large, is the Boston Journal of Chemistry.

A new journal, The Scientific Monthly, devoted to the natural and kindred sciences, has recently been started at Toledo, Ohio. Mr. E. H. Fitch, Editor.

"Transactions of the American Dental Association for 1875," received. Good paper, type, and very valuable.

"Transactions of the Pennsylvania State Dental Society for 1875." Well gotten up, and containing valuable essays and dis

cussions.

THE MISSOURI

DENTAL JOURNAL,

A MONTHLY RECORD OF THE SCIENCE.

VOL. VIII. APRIL, 1876-No. 4.

CYLINDER FILLINGS.

BY C. W. SPALDING.

Of all the older methods of manipulating foil in the filling of teeth, that known as the cylinder method appears to be the one most likely to survive, and to successfully compete with those of more recent date. And why is it that this method bids fair to outlive the others? The answer is plain. It is because it possesses merits not possessed by either of the other older methods. One of the merits claimed for the cylinder method is that of great durability, especially in grinding surfaces, where the attrition of mastication subjects our operations to the test of both density and thoroughness. The writer has in his possession specimens of this kind of filling that have endured the wear and tear of from 25 to 35 years of hard service, and are still sound and perfect, and apparently would have lasted for another equally long period of time. Another meritorious point is, that this method necessitates a more thorough and consequently a better preparation of cavities preparatory to receiving the gold than is usually practiced. If this latter claim is well founded, the point