Strange to say, Lord Rodney was a most strenuous advocate for the slave trade! His great argument in its favour was, that if negroes were not allowed to be imported into the West Indies, the labour which their tribes executed there must be performed by indentured servants, the result of which would be an injurious decrease of the population of these kingdoms! This it is for Admirals to become politico-economists!

ART. X.-Annuaire pour L'An 1831, Presenté Au Roi, par le Bureau des Longitudes. Paris: Bachelier, Pere, et Fils. 1830.

A COMPARISON of the rate of mortality, and of the growth of population, in London and Paris, cannot fail to be generally interesting. We have, in the valuable little work before us, together with similar accounts for France generally, tables of the deaths and births, which took place in Paris, in the year 1829. The number of births, during that period, appears to have been,―males, 14,760-females, 13,961-total, 28,721. The number of deaths, was 25,591, of which 12,239 were those of males, and 13,352 females.

For the same period, we find the number of children christened in London, to have been,-males, 13,674-females, 13,354-total, 27,028; and the number of persons buried, to have been,-males, 12,015-females, 11,509-total 23,524. The reader will be struck with the almost identity of the number of births in the two capitals, and he will naturally ask, is Paris as populous as London? The answer is, that it is not; and the reason why this equality, as to the number of inhabitants appears, is, that in Paris, no births or deaths whatever are omitted in the register, whilst in London, those are excluded, which take place in the families of persons of certain religious persuasions, or who do not reside within, what are called, the bills of mortality. But still, upon the given amount of births and deaths, in both cities, we can establish a very fair comparison between them, in many respects. We see, in the first place, that the year 1829, had added to the population of Paris, 3130 persons, while it has given to a less amount of population (by 1693 individuals) in London, 3504 inhabitants. The number of females, born in Paris, was considerably less, in regard to that of males, than in London, where the births of persons, of both sexes, were not far from being equal, the small difference being in favour of the males. The deaths in Paris, were greatest amongst the females, whilst in London, they were most amongst the males.

We happen to have before us, the return of the bills of mortality, of London, for the year that is just over, and in this document, we discover, that the number christened, in 1830, was--males, 13,299 -females, 13,444-total, 26,743; being a decrease of births chiefly

in the male sex. The burials were, males, 11,110-females, 10,535 -total 21,645; which leaves an addition of 5098 inhabitants to the population of 1831. This is a vast difference for one year to make. But we should say that, with respect to the mere question of increase of population, London far outstripped Paris. The inhabitants of the latter city are comparatively stationary, and we believe, even, that such improvements as are or have been going on there, tend rather to thicken residents, on a given spot, than to disperse them. In London the case is the reverse. The old streets are constantly losing their inhabitants. The city of London-the antiquated part of it, is hourly thinning, and this is especially the case with respect to those parishes which are strictly within the verge of the bills of mortality. The conclusion then is, that London, which thus undergoes a constant drain of the sources of a fresh supply of population, still is able to make a more respectable figure in its increase than Paris, with all its advantages.

We have no account of the causes of the deaths in Paris, nor of the ages of the persons dying. The Catalogue Raisonnée of the triumphs of diseases in London, which is furnished annually, by those wonderful adepts in diagnosis and pathology—the parish clerks we are afraid, is not a document that will obtain any great degree of confidence with the world. However, we may mention as a curious, and, we hope it will prove to be, a useful fact, that whilst the deaths on account of small pox in London are set down, in 1830, as 627, the deaths from the same cause, in Paris, are marked as no more than 283. We are very much surprised at the difference. When we consider the density of the population of Paris, or rather the state of concentration in which its inhabitants may be said to be collected, we cannot imagine how it is possible that a contagious disorder, like the small pox, could be arrested in such a place, if once introduced, without doing much more extensive mischief than we find to be the case. However, we believe that much of the impotence of small pox in Paris, is to be attributed to the vigilance of the authorities, and their determination to execute the law with fidelity. We remember, some years ago, seeing a proclamation of the Archbishop of Paris, in which he signified that the rites of the church would be withheld from all parents who knowingly allowed their children to go beyond a certain age without vaccination. We shall have an opportunity of discussing the questions connected with this subject, when the population returns from England and Scotland, which are to commence in May next, shall have been completed. In the mean time it may not be uninteresting to state the account of marriages in Paris, in 1829.

It would appear, therefore, that the French widows are much more constant to their first flames than the widowers, for whilst 901 of the latter embraced matrimony more than once, of the former there were only 440 who possessed the same temerity. The following conclusions, drawn by an ingenious and industrious mind, from authentic data, relative to the statistics of Great Britain, must prove interesting:

The number of men, from 15 to 60 years of age, is 2,244,847, or about 4 in every 17 males. There are about 90,000 marriages yearly, and of every 63 marriages, 3 only are observed to be without offspring. The deaths every year, are about 332,700; every month, about 25,592; every week, 6,398; every day, 214; every hour, about 40. The proportion of the deaths of women to those of men, is as 50 to 54. Married women live longer than those who are not married. In country places there are, on an average, 4 children born of each marriage; in cities and large towns the proportion is 7 to every two marriages. The married women are, to all the female inhabitants of a country, as 1 to 3; and the married men to all the males, as 3 to 5. The number of widows is to that of widowers, as 3 to 1; but of widows who re-marry to that of widowers, as 4 to 5. The number of old persons who die during the cold weather, is to those who die during a warm season, as 7 to 4. Half of all that are born, die before they attain 17 years. The number of twins is to that of single births, as 1 to 65. Old Boerhaave says, the healthiest children are born in January, February, and March only 1 out of 3125 reaches 100 years. The greatest number of births is in February and March. The small-pox, in the natural way, usually carries off 8 out of every 100 it attacks; by inoculation 1 dies out of every 300. The proportion of males born to that of females, is as 26 to 25. In our sea-ports, there are 132 females to 100 males, aud in the manufacturing towns, 113 females to 100 males.

ART. XI.-The Cabinet Cyclopædia, Vol. XIV. A Preliminary Discourse on the Study of Natural Philosophy. By J. F. W. Herschel, Esq., M.A. London: Longman and Co. 1831.

To combine profound and minute knowledge of difficult sciences with the art of perspicuous and agreeable writing, is so very rarely achieved in these days, that we cannot too much prize so happy a conjunction when it occurs; and it is on this account, that we think we are authorised to declare this little book by far the most delightful, (considering its subject), to which the existing competition between literary rivals of great talent and enterprise has given rise. To say the plain truth, we often were inclined to believe that Milton's speech, about the musical attractions of philosophy, was only an allowable figure of rhetoric, not to be curiously criticised, as coming from a great poet. We believe that many would be ready to join us in our notions, unless, indeed, they have, with us, had the opportunity of learning, in the pages of Mr. Herschel, the

realization of the oracle of the immortal bard, for truly may we, indeed, say, that philosophy is no longer that rugged and revolting study" which dull fools suppose," but that it is as musical as Apollo's lute.

Setting aside the merits of this Discourse, as a collection of singular and important facts, interesting to every human being, we should say that, as an example, or rather a model, of the true plan of illustrating principles, it is without a rival, with the exception perhaps of Dr. Arnot's masterly work on physics. It does not propose, in any instance that we can discern, to explain one difficulty by citing another, which is sure to be still more insurmountable. It does not, like some of our modern performances in the same way, come under the objection of the Gentleman in the Critic, who declared that the interpreter was the more difficult to be understood of the two. From this time forth, therefore, we may expect to see our scientific literature, we mean, especially, that portion of it destined for the instruction of scholars who do not go to school,-assuming the real simplicity and clearness which it ought always to have possessed, and of which Mr. Herschel has now sent forth a brilliant, and, we hope it will prove, an exemplary sample.

The Discourse is divided into three parts, in the first of which the author descants on the nature and advantages of the study of the physical sciences, a theme rendered hazardous and difficult, after having been so recently presented to the public, clothed in all the hues of the splendid mind of Lord Brougham. Mr. Herschell, however, has contrived to give fresh ornaments to the subject. In speaking of the power of abstract reasoning, which, without experience, will determine important conclusions as the results of new combinations, and will, as it has often done, absolutely correct hasty and unskilful experiments, the writer furnishes this happy illustration. The subject is one upon which Mr. Herschel is particularly conversant, he having made some very curious discoveries in connection with it.

Every body knows that objects viewed through a transparent medium, such as water or glass, appear distorted or displaced. Thus a stick in water appears bent, and an object seen through a prism, or wedge of glass, seems to be thrown aside from its true place. This effect is owing to what is called the refraction of light; and a simple rule, discovered by Willebrod Snell, enables any one exactly to say, how much the stick will be bent, and how far and in what direction the apparent situation of an object seen through the glass will deviate from the real one. If a shilling be laid at the bottom of a bason of water, and viewed obliquely it will appear to be raised by the water; if instead of water spirits of wine be used, it will appear more raised, if oil, still more; but in none of those cases will it appear to be thrown aside to the right or left of its true place, however the eye be situated. The plane in which are contained the eye, the object, and the point in the surface of the liquid at which the object is seen, is an upright or vertical plane; and this is one of the principal characters in the ordinary refraction of light; viz. that the ray by which we see an

object through a refracting surface, although it undergoes a bending, and is, as it were, broken at the surface, yet, in pursuing its course to the eye, does not quit a plane perpendicular to the refracting surface. But there are again other substances, such as rock-crystal, and especially Iceland spar, which possess the singular property of doubling the image or appearance of an object seen through them in certain directions; so that instead of seeing one object we see two, side by side, when such a crystal or spar is interposed between the object and the eye: and if a ray, or small sun-beam be thrown upon a surface of either of these substances, it will be split into two, making an angle with each other, and each pursuing its own separate course-this is called double refraction. Now, of these images or doubly refracted rays, one always follows the same rule as if the substance were glass or water: its deviations can be correctly calculated by Snell's law above mentioned, and it does not quit the plane perpendicular to the refracting surface. The other ray, on the contrary, (which is therefore said to have undergone extraordinary refraction) does quit that plane, and the amount of its deviation from its former course requires for its determination a much more complicated rule, which cannot be understood or even stated without a pretty intimate knowledge of geometry. Now, rock crystal and Iceland spar, differ from glass in a very remarkable circumstance. They effect naturally certain regular figures, not being formed in shapeless lumps, but in determinate geometrical forms: and they are susceptible of being cleft or split much easier, in certain directions, than in others; they have a grain which glass has not. When other substances having this peculiarity (and which are called crystallized substances) were examined, they were all, or by far the greater part, found to possess the singular property of double refraction: and it was very natural to conclude therefore, that the same thing took place in all of them, viz. that of the two rays, into which any beam of light falling on the surface of such a substance was split, or of the two images of an object seen through it, one only was turned aside out of its plane, and extraordinarily refracted, while the other followed the ordinary rule. Accordingly this was supposed to be the case: and not only so; but from some trials and measurements purposely made, by a philosopher of great eminence, it was considered to be a fact sufficiently established by experi

ment.

Perhaps we might have remained long under this impression, for the measurements are delicate, and the subject very difficult. But it has lately been demonstrated by an eminent French philosopher and mathematician, M. Fresnel, that granting certain principles or postulates, all the phenomena of double refraction, including perhaps the greatest variety of facts that have ever been arranged under one general head, may be satisfactorily explained and deduced from them, by strict mathematical calculation; and that, when applied to the cases, first mentioned, those principles give a satisfactory account of the want of the extraordinary image : that, when applied to such cases as those of rock crystal or Iceland spar, they also give a correct account of both the images, and agree in their conclusions with the rules before ascertained for them: but so far from coinciding with that part of the previous statement, which would make these conclusions extend to all crystallized substances, M. Fresnel's principles lead to a conclusion quite opposite, and point to a fact which never