Appendix to Mr. Park's Travels, page 26.

+ The places of observation are marked on the map by asteriską.

settles in the water to her load water-line, let each of these tunnel. holes be successively plugged up. When the Ship floats at her load

water-line, she will contain a quantity of water equal to her internal capacity, which is her tonnage: then let all the salt or fresh water she contains be pumped out into tubs, containing half a ton each; and when all the water is pumped out, her exact tonnage will be known, es also her best sailing trim in every gradation of her immersion, from her light water-line, to her load water-line.

N. B. As salt and fresh water differ in weight, the tubs must be proportioned accordingly.

Thirdly,-Take a quantity of iron ballast whose weight is known, and load the Ship with it to her load water-line, which will give her internal capacity. That calculation is best which comes nearest to the tonnage given by these methods.

N. B. The above is intended as a general treatise on the property of Ships; but should any person be desirous of obtaining accurate information respecting Ship-building, I beg leave to refer them to the regular publications of the SOCIETY FOR THE ENCOURAGEMENT OF NAVAL ARCHITECTURE.

[To be continued occasionally.]

L.

[Copied by Permission from Major Rennell's Appendix to Mr. PARK's Travels.]

AGREAT part of Mr. Park's geographical memorandums are

totally lost; but fortunately his bearings by Compass during a great part of the way, are preserved. In other parts he has preserved only the calculation of latitude and longitude, arising from them; which, however, of course furnish the means of obtaining the bearings, if necessary. As he omitted to take observations to determine the quantity of the variation of the Compass, after he lost the means of correcting his course by observations of latitude, which was at Jarra, about midway in his route t: it becomes a question of some importance, what quantity to allow on those long lines of distance between Jarra and Silla; Silla and Manding.

It appears on inquiry, that the quantity of variation is no more known any where within the continent of Africa, than within that of New Holland. And it happens moreover, that the lines of equal quantities of variation, do not run across Africa with that degree of

Appendix to Mr. Park's Travels, page 26.

+ The places of observation are marked on the map by asterisks.

regularity and parallelism, which takes place over great part of the Atlantic and Indian Oceans fat least this is what appears clearly to my judgment) so that it became necessary to enquire, what quantity prevails in the surrounding seas; and what the general direction, as well as the particular nature, and tendency, of the curves, of the lines of equal quantities.

The variation lines on the globe have occupied a good deal of my attention, at different periods of my life; and therefore the application of such new observations, as the assiduity and kindness of my friends had procured for me on this occasion, was less difficult, than if the subject had been new to me. A dissertation on the subject, would be out of place here; and therefore I shall only give the result of my inquiries, in abstract; after premising, that the theoretical part belonging to the interior of Africa, is founded on a supposed continuation of those lines of equal quantities; whose tendency has been already ascertained, in the surrounding seas. I am perfectly aware, that some may regard the assumption as too great but they will no doubt admit, at the same time, that it is difficult to conceive a more probable arrangement and what is much more to the purpose, is, that if we are compelled to abandon the system, in the gross, the quantity of variation in the line of Mr. Park's travels, cannot be greatly different from what we have assumed. For, whether the line of 18 degrees in the south Atlantic, be a continuation of that in the north Atlantic, or of that in the Indian Sea, much the same result will follow only that in the former case, the quantity will be somewhat greater.

It would appear, that between the East Indies and South Ame rica, Europe and South Africa, there are four distinct sets of what may be termed concentric curves of variation lines, on the globe; and whose highest points of convexity are opposed to each other, within the great body of Northern Africa. The accompanying sketch will Best explain it. It would appear moreover, that from the place of

This sketch is not pretended to be minutely accurate; it being morally impossible to procure resent observations in every part, from the rapid change that takes place in the quantity of the variation, in one and the same spot. However, the observations that determine the course of the lines in the Atlantic (and which are marked on the sketch) are from observations so late as 1793The same is to be said of those in the western quarter of the Mediterranean and those beyond the Cape of Good Hope, to longitude 30 degrees east, are of the year 1789.

It is obvious that a critical knowledge of the quantity of the variation in any particular place, and at a given time, is of less importance to the present question, than that of the bearing of the lines of equal quantities, at any recent period and this object is, I think, tolerably well obtained by the materials before me. Any change that may have taken place since 1793, is in favour of a greater quantity of variation, within the limits of Mr. Park's travels.