man. We see therefore that every thing reduces itself to the means which geometry furnishes. What is it which this science proposes? The measure of every thing which exists in the sensible world. That which exists is the work of nature, who has concealed throughout the simplicity of her principles under a variety of phenomena of nature, who, by opposing secondary principles, by making one thing act upon another, has appeared to disturb the prevailing uniformity and regularity, and has nowhere inade two forms alike, or one that is regular. Man loses himself in this infinite variety. That which is much compounded is no longer regular with respect to him. He requires simple things and such as may be arranged according to his manner of conceiving them. We have undertaken, in order to study nature, to measure her works, by applying to them the figures of geometry, the regular forms of which we know the law. Able to multiply and vary these almost at pleasure, we can, by repeated attempts, imitate in our measures, the things we would know, we can approach in our copy of this grand model, almost as near as we please to the original, without ever reaching it perfectly. Indeed although the world presents no where lines absolutely straight, surfaces exactly plain, regular triangles, squares or cubes. perfect circles, ellipses, or parabolas, we measure by means of these figures an infinite variety of spaces that depart from them but a little; and when we endeavour thus to descend to details and to reach more nearly the truth of things, we require forms less simple and curvatures more complicated, to appreciate these very departures.

Moreover, when Newton applied geometry to the mechanical phenomena of the heavens, and raised the science to this great height, it became necessary to compare together things that are not of the same nature. Motion takes place in space, it lasts for a time, it has a velocity. Space, time, velocity, have no resemblance to each other. If velocity is the more rapid, according as the space passed over is greater, and the time employed less, what relation have time and space with each other? Yet geometry can be applied only to relations and equalities. We arrive at a comparison between things of a nature so different, by establishing for each of them a different modulus, a particular unit; and when we compare velocities, times and spaces, the comparison of each of these quantities with its particular modulus is always understood. We say for instance with respect to motions that are uniform, that when the times are equal, the spaces are as the velocities. These suppositions together with a few simple principles make the basis of the science of bodies in motion, a science created by Newton, and called dynamics, but which we have here com. prehended under the general denomination of geometry.' vol. ii. pp. 378-383.

The other discourses of our author are distinguished by the same original manner of thinking and writing. This part of the work is free from that spirit of system which pervades and mars a very considerable proportion of the res. The great excellence of the whole is, that without being superficial it is adapted to common readers and calculated to interest them. The author selected the most striking parts of his subject, and has presented them with great amplification, and great force and beauty of language. Many may here become acquainted with the leading truths of the science, and may be made to feel their importance and sublimity with very little exertion and little preparatory study.

&. Hale.

ART. IX.-A Letter on the Fellow Fever of the West Indies. By Daniel Osgood, M. D. Practitioner of Medicine in the city of Havana. pp. 72. E. Bliss, New York, 1820.

SINCE the notice which was taken of the subject of the contagion of yellow fever, in our number for April last, we have received still further confirmation of the general correctness of the opinions which were then expressed. The circumstances connected with the appearance of this disease, in some of our cities the last summer, furnish very decisive evidence that it was not propagated by contagion.

In Philadelphia, where the health regulations were last year entirely founded upon the supposition of contagion, the good effects of acting upon a contrary belief this year, while the fever prevailed there, seem to have removed almost every fear of its possessing any such property. If it were true that those who are affected by it communicate the disease by its contagious poison to those about them, what method could be devised more calculated to spread the disease in every direction, than removing the sick, and scattering them among those in health? Yet it is well known to every one, how opposite to this was the result in Philadelphia, as it was in other places the previous year. It cannot be doubted that it is owing to the wise precaution of removing all persons, both sick and well, from the sickly neighbourhood, that the ravages of the disease were so limited and so speedily checked. Had the same course been adopted, that was pursued in the fever of 1793, there is much reason to apprehend that the disease would have been equally destructive.

In New York the very rigour of their quarantine and nonintercourse system has furnished some striking proofs of its inefficiency and uselessness. Not the formidable parade of proclamations prohibiting the entrance into the city of any person or thing, which had been within thirty days in Philadelphia, not the city marshals posted at every avenue to enforce the exclusion, nor the keenness of perception of the health physician, so sharpened by his apprehensions as to espy symptoms of yellow fever in the common effects of a debauch, could prevent the introduction of a few cases of the disease. And yet it was not communicated, even to the friends and attendants of the sick.

There is a curious contrast of circumstances, as they occurred in New York and in Baltimore, while the alarm of fever prevailed in Philadelphia. In the former city, while every thing coming from the seat of the disease was excluded with a vigilance worthy of a better cause, several cases of the fever occurred, and the whole city seemed constantly in a state of agitation and alarm; but in the latter, with no interruption to the free communication with Philadelphia, there appears to have been no case of the disease, and no apprehension or alarm. We confess we feel very little sympathy for the disappointment of the friends of contagion in New York, in the failure of their prohibitory schemes. Had they been willing to learn it, the occurrences of the previous year would have taught them the impolicy of relying upon such means of prevention. We cannot, however, but lament their want of success in their attempt to check the progress of another disease, for which it seems the quarantine system is unfortu nately equally ineffectual. Happy would it have been for New York, happy for our country, had this experiment but succeeded, and proved that the dreadful contagion of intemperance could be destroyed by a thirty days' quarantine.

The author of the pamphlet before us has not entered into a discussion of the question respecting the contagious nature of yellow fever. He, however, very fully declares his opinion against the supposition of contagion. In an introductory letter to Dr. Perkins he says,

Although, as you will perceive, I have rather avoided all controversial remarks, on the identity of the disease in different countries, and on the question whether it be from a contagious cause or not, yet I feel it my duty, so far to answer your inquiries on

these points, as here to state, that, regarding its character both within the tropics, and in the higher latitudes, where I have been acquainted with it, I have not been able to discover any other varieties of its symptoms, than such as I conceived to have arisen from the differences of constitution, exposure and treatment in those affected by it, and from changes in the weather. Nor have I seen an instance, during nearly twenty years' constant practice in this disease, in which it appeared to me to be communicated from one person to another; or of its having originated from any exposure whatever, except in places peculiarly circumstanced.' p. iv.

The experience of a man of observation, during so long and extensive a course of practice, might justly be relied upon as of much authority in a question of this sort, and were it not for the overflowing abundance of proof, of a more positive nature, of the absence of contagion in this disease, we might quote this declaration as a farther confirmation of the correctness of our positions.

The principal design of this pamphlet appears to be to give the observations which the author's practice has enabled him to make on the symptoms and character of the yellow fever and the mode of treatment best adapted to it. As the nature of the disease has been so fully investigated and described by a great variety of physicians, much originality were not to be expected, especially as the author has not accompanied his description by any dissections, by way of illustration of its character. It is in this more than in any other particular, that our knowledge of the phenomena of the disease is deficient. The description of the symptoms and cure is clear and satisfactory. One feels as he reads it, that the author is relating what he has himself seen and done, and not what he has learned from others.

Probably few physicians of the present day would entirely agree with our author, as to the causes of yellow fever. His account of the manner in which these causes operate to produce the disease is in true Brunonian style.

In situations,' he remarks, and under circumstances before described, as exposing to the yellow fever, the subjects experience, for a while, an increased excitement in all the organs of the body, whether animal, natural, or vital; expending the excitability equally throughout the whole system; but subsequently the stimulus of heat, &c. acting directly on the organs of the vital

functions, continues to support their increased excitement, while the organs of the animal and natural functions have their excitability still wasted, without a proportionate supply of the same strinuli This state of the system clearly constitutes the disease in its more moderate degree; but when the malignant form occurs, it happens from an early derangement in all the functions together, by a direct exhaustion of the general excitability.' p. 26.

It is unnecessary, although it would be easy, to show how far this is from an explanation of the phenomena of the dis

ease.

By far the most important part of this treatise, in our view, is the section on the Prevention of the yellow fever. Thousands of persons go from this country and other temperate climates to the West Indies, and are there cut off in a short time by this formidable disease. Many of these lives might doubtless be saved, if a proper course of regimen were followed, during the earlier period of their exposure in a tropical climate. We could wish that some person as well qualified for the task, as the author of this letter, might be induced to pursue this subject further, in a form adapted to the situation of the classes of people most nearly interested in it. It is not to physicians, but to merchants and seamen that such a work should be chiefly addressed. It should therefore be a distinct treatise, and independent of all such speculations as are interesting only to physicians. Such a treatise if properly executed, we are persuaded would be extensively useful, and furnish an ample remuneration for the labours of its author.

Appended to the letter of Dr. Osgood is an extract of a letter from Cyrus Perkins M. D. city of New York, on the distinction between contagion and infection. Although we are not quite satisfied with the common use of the term infection, we are not disposed to question the general accuracy of this gentleman's opinion on the subject. But there is one remark which appears to us entitled to a more distinct notice. For my own part.' he says, although I early made up an opinion on the subject, I never had so chivalrous a disposition as to enter the lists for making proselytes. And I have often thought, that, if the disputants by way of preliminary, were first to agree on a precise definition of terms, they would find but little left to dispute about.'