experiments stated: and that the third supposition is not, is evident from the following experiment. The plus and minus resistance of a parallelopipedon one foot square immersed to the depth of very nearly six inches, and moving with a velocity of 12 feet in a second, is 152.62 lbs. avoirdupois; and in table 2d, the resistance of a plane containing one superficial foot immersed to the depth of six feet, and moving with a velocity of 12 feet, is 157.20 lbs., which is not widely different; and this variation of 4.58 lbs. may partly be attributed to the longer body being less resisted than the plane.

The first column of the following table contains the velocity in feet per second; and the second column contains the friction of water against 100 superficial feet of wood immersed to the depth of six feet; and great pains were bestowed in rendering the surface of the wood as even and smooth as possible.

The third column contains the increase of the friction by sinking the surface one foot lower. If the friction be required for nearer the surface than six feet, the numbers in this line must be subtracted from those in the first line; but if lower be wanted, the numbers in this line must be added. These numbers were determined from actual experiment.

By this table a judgment may be formed what is the friction of the water on the bottom of a large ship; or, more properly speaking, what is the minimum of the friction; for it is almost impracticable to render the immersed part of any vessel so even on the surface as that with which the experiment was made.

A second rate man-of-war has 15,000 superficial feet immersed under the water, if the draft of water be 24 feet. Supposing the vessel sails at the rate of 20 feet per second, and that the friction is calculated at the depth of 12 feet, or half the draft of water, then 121-8624-668 = 146 53, which, multiplied by 150, gives 21979 lbs. or somewhat more than nine tons; but in fact this additional resistance to the division of the fluid must be far greater, as a vessel when coppered is, comparatively speaking, a very uneven surface; and any contrivance to diminish the friction would be very desirable. Rolled or milled copper sheets being smoother than those hammered, if one of his Majesty's ships had one side coppered in the usual manner, and the other side with rolled or milled copper; pains being taken to lay the sheets on as evenly as possible, and the heads of the nails countersunk; if this vessel so prepared were sent to sea in company with another, and under favourable circumstances, the two vessels, by setting more or less on the same tack, had equal progressive velocity; and the two vessels put about, and run on the other tack with the same quantity of sail; the difference of the sailing will show the advantage of the two modes of coppering.

Friction of the Water against 100 Feet, at the mean Depth of

6 Feet.

From these experiments, it is evident that the resistance a body meets with when moving in water consists of three parts-the head resistance, the minus pressure, and friction.

The shape of the solid of the least resistance is still to be ascertained, which experiments alone can determine; though perhaps no shape will answer in every velocity.

I remain, my dear Sir,

Yours very sincerely,

MARK BEAUFOY.

ARTICLE V.

New and important Combinations with the Camera Lucida.
By W. G. Horner, Esq.

(To Dr. Thomson.)

SIP,

Bath, Aug. 15, 1815.

THE numerous inventions of Dr. Wollaston in various depart ments of philosophy are marked by that precision and completeness which constitute the true idea of elegance. They seldom leave to succeeding experimenters any hope of adding an improvement, and are only capable of being enhanced in estimation by multiplying the useful purposes to which they may be applied. These remarks are eminently appropriate to the Camera Lucida. As a corrective of the erroneous decisions of the eye, or a succidaneum to the labour of educating that organ, the utility of this beautiful little machine is well known. These advantages, offered by the instrument in its simple form, have been proved by the geologist, as well as by artists in miniature, landscape, and architecture; but I am ignorant if any philosopher has been struck with the still more extensive uses to which it may be adapted in combination with the microscope and telescope.

Many circumstances occur to recommend these adaptations, without including the superior gratification of being able to copy with certain correctness the forms of minute or inaccessible and distant objects, when compared with that of retailing appearances, which are open to every beholder. The great difficulty which even an experienced artist finds, in representing with tolerable accuracy a telescopic or microscopic image viewed in the usual constrained and interrupted manner, will render this improvement highly desirable. The astronomer, and even the military officer engaged in reconnoitring, would derive important assistance from the use of the graphic telescope.

The patent for the Camera Lucida remains, I believe, with the illustrious inventor; and his sagacity, which has perhaps anticipated the hints conveyed in this paper, will immediately discover the best methods of applying them to experiment. Those methods which I take the liberty of noticing are simple, and such as I have partially submitted to trial.

The obvious principles which require attention in both the adaptations recommended are, to immerge the object-face of the prism into the cone of distinct rays which issue from the eye-glass of the other instrument, further than is permitted by the usual eye-piece; and to allow a close approach of the eye to the upper surface of the prism. These precautions evidently tend to secure a sufficient extent to the field of view.

The graphic microscope would perhaps be constructed in the best manner by attaching a single microscope to the object-face of the prism. The appendages of pliers, &c. might be made applicable to the shaft or style of the camera. The vertical structure, and other properties of the compound microscope, present obstacles which it would not be easy to surmount. And the solution of these difficulties is the less necessary on account of the facility afforded by the construction of the camera lucida itself, for enlarging or contracting the dimensions of the apparent image at pleasure.

In the telescope the perforated cylindrical cap, which is screwed over the eye-glass, may be exchanged for a shorter, conical, or cuneiform cap, having a larger aperture. This cap might carry an arm, perforated to admit the axis of the prism. A still preferable method is, to take off the perforated cap, and attach a hollow tube to the side of the eye-piece. In this tube, which must of course be shorter than that in which the stem of the camera slides, a similar stem must be inserted bearing the prism: in short, the original instrument, cut off at one third of its length, must be attached to the tube which contains the eye-glasses of the telescope. The telescope being adjusted to a proper focus, and the stem of the camera drawn out to a due length, and turned, to bring the prism opposite the axis of the telescope, the aperture of the eye-piece of the prism being also placed in such a manner as to exclude, if requisite, the superfluous rays; the objects toward which the instrument is directed will appear, on looking through the prism, to be

distributed over the paper which is placed to receive the design. I. will be necesssary to support the paper as nearly as possible paralle to the axis of the telescope.

If you judge these observations deserving of public diffusion, they are much at your service; and a candid notice of them in your Journal, will oblige,

Sir, your most obedient servant,

W. G. HORNER.

ARTICLE VI.

An Attempt to systematize Anatomy, Physiology, and Pathology. By Alexander Walker.

SIR,

(To Dr. Thomson.)

THE value you yourself have attached to the systematization of chemistry convinces me that you will not view with disregard a similar attempt in anatomy. To you I need not say that the placing on the title-page of a work the word "System," does not convert the ill-arranged facts and reasonings of any science into a real system. That word expresses the arrangement of these facts and reasonings according to their natural relations; and in that sense there is certainly no system of Anatomy. In that science, the discovery of these natural relations has long been an object of my investigation; and the views I have taken in the present paper being to me more satisfactory than any which have hitherto suggested themselves to me, I shall be happy if they prove not unsatisfactory to your readers.

The arrangements of the present paper being intimately allied with, and in a great measure founded upon, the facts and reasonings contained in my Sketch of a General Theory of the Intellectual Functions of Man and Animals, inserted in two of your former numbers, the simplicity, the accuracy, and the extensive applicability, of these arrangements, will afford the best and most striking proof at once of the truth and of the originality of that theory.

It is unquestionable that a correct arrangement of anatomy and physiology, or rather of the organs and functions which they consider, ought to indicate, at a single glance, the relations of all these organs and functions to, and their dependence upon, each other. Yet is this principle uniformly violated by the best anatomical and physiological writers.

A single remark will at once point out the errors of arrangement which I deprecate, and show the originality of the plan which I propose. It is evidently unnatural to consider the brain before the organs of sense whence impressions are transmitted to it; the organs

of generation, before the glands whence they derive the generative liquid; the glands, before the arteries whence is received the liquid they transmute; the arteries, before the heart which is the source of the blood they circulate; the heart, before the absorbents whence the materials of the blood-the chyle and lymph, are derived; the absorbents, before the stomach where is digested the food whence the chyle and lymph are elaborated; or the muscles, before the ligaments, by which their motions are limited, and without which they cannot be understood. Yet are more or less of these errors committed by Soemmerring, Blumenbach, Hildebrandt, Winslow, Sabatier, Cuvier, Chaussier, Boyer, Dumas and all the best anatomical and physiological writers.

Nor is this all: not only do they, with regard to the organs and functions, reverse, often to a great extent, the order of their dependance, but they widely separate objects which are in nature closely connected, and blend together others which, belonging even to distinct classes, have little natural relation. If the arrangement of the author of the Tables Synoptiques de l'Anatomie, in particular, were to be considered, as all arrangement ought to be, namely, as indicating the relations and dependance of the functions, so absurb is it, that absorption, instead of the cause, would be the result, of nutrition; generation, the result of absorption; and digestion, the result of generation.

Thus by arranging effects in the place of causes do physiologists confound the relations of the functions, and reverse the very order of their dependance.

The general arrangement of the functions into external, relative, or animal, and internal, assimilating, or vegetative, as anciently proposed by Aristotle, and successively adopted by Buffon, Grimaud, and Richerand, is replete with error.

For, first, under the term external, relative, or animal functions, are thus involved, not only the intellectual actions, consisting of sensation, thought and volition, but the locomotive actions by which we move from place to place; yet these actions differ from each other in every respect. They do not resemble each other in their intimate nature; for the intellectual take place longitudinally,* and are altogether invisible; while the locomotive are performed angularly by means of levers, and are of the most conspicuous kind. Neither do they agree in being both external; for the locomotive can alone be considered so, while the intellectual are as internal as the animal or vital, on which these physiologists have improperly conferred that epithet. True it is that the eye and the ear, which are intellectual organs, receive impressions from external objects; but so do the absorbent surfaces, which are vital organs. If it be urged that the absorbed matter is carried inward to the heart, so must it

* In the tubes of the neurilema.

+ The bones.