will not happen once in fifty labours, and, when neceffary, are not to be performed in the manner he recommends, by turning the four fingers and thumb clofed lengthways, and turning them backwards and forwards. Nor is the perinæum (which he calls the feam of the hips, a term, as well as many others, abfolutely unintelligible on this fide the Tweed) to be faved by the me thod he here recommends; on the contrary, it will rather endanger the tearing it more. And as this circumftance of lacerating the perineum is the most common accident in labours, especially of firft children, our author, who enumerates many of lefs confequence, would have done well to have mentioned the means of preventing it,

At p. 59. 1 18. to p. 60. l. 13. we find the following paffage:

Eighthly, After the child is born, if the womb-cake or after- birth comes quickly away, as generally happens in natural births, and the child is living and well, we forthwith tie and cut the navel-ftring, and order the child's head to be covered with a warm cap, and put under the bed-clothes, or its body to be covered with a warm flanuel or linen cloth.

If there is no token of the after burden coming away foon, and no flooding obliges us to haften its delivery, we rather let it alone a while, and allow the mother to rest a little, and the child recover.

If the child happens to be born very weakly, before we tie and cut the navel-firing, we deliver the after-burden.'

It fometimes happens that the after-birth immediately follows the child, in which cafe there is no time to tie the navelfiring and feparate the child before the after-birth comes away; but this does not happen once in five hundred labours. In all other cafes the best practitioners recommend the feparating the child before any attempt is made to bring away the placenta. By the natural contraction of the womb, when freed from the diftention occafioned by the bulk of the child and waters, the after-birth is kindly and gradually feparated; but this does not happen inftantly; and if there is no flooding, we may safely wait half an hour; but furely, whether the child is born weakly or not, there is no occafion to defer the separation of it: no benefit can accrue to the child, none to the mother; but many to both, by making a fingle ligature and dividing the ftring, which it is not our present bufinefs to enumerate. The arts commonly used to revive a weakly child can be better put in practice on the nurfe's knee by the fire fide: and indeed when our author comes to treat of the manner of delivering the placenta, he takes it for granted that the navel-ftring is tied and cut before that is attempted. We obferve that our author has herein been influenced by Dr. Smellie's first publication ;

we know too that Mauriceau and others recommend the fame practice; notwithstanding which, we will venture to affirm the other to be by much the better method; and that it is now adopted by the ableft practitioners of this kingdom, both male and female.

The great objection we have to this work is, that it seems entirely to be copied from books, and not dictated by experience ; and that oftentimes dangerous, if not impoffible ex-' pedients are recommended; as for example; At p. 53, in the cafes of difficulty, after the head of the child is born, he expreffes himself thus; or fhould the outward mouth of the womb be ftrongly contracted round the neck, we push up our hand along its breaft, and pull as before.' In this fituation it is very difficult to push up the hand, and the consequence of attempting it will certainly be the tearing the perinæum, or hip-feam, as our author terms it. At the bottom of p. 64. he' fays, the washing of the child may be performed first, before the navel-ftring is tied and cut, for which he may have fome written authority, but, however, we do not remember it; and we will venture to affert the practice is both difficult and' abfurd. The last thing that we must disapprove in this first part on natural births, is his advifing the hand to be paffed up into the womb after the delivery of the placenta; for notwithstanding this practice has many abettors, there can happen very few cafes indeed in which it is neceffary; and to recommend it in all, is giving the mother unneceffary pain, and may be productive of danger.

We fhall be very concife on the remainder of this work, declaring before hand our total disapprobation of putting the inftruments he mentions into the hands of the female practitioner, and expreffing our wishes that they were not fo often used by the males, which publications of this nature are too apt to promote. With regard to the ufe of the forceps, he fets out with the following directions;

Having first anointed our hands, and the outward mouth and paffage of the womb, with hogs-lard or foft fresh-butter, we ftretch the fame flowly and gradually with the fingers of our right-hand, one after another, and then altogether, introduced in a longifh form, and turned round backward and forward, pushing up more and more by piece-meal, till the parts be fufficiently widened, as was fhewn before in natural births.

If the head of the child is fo low, that our hand cannot be introduced high up in this form, we widen the passage with our fingers pushed up along the moveable end of the rump-bone, the back of the hand being placed next to the child's head;

and

and when fufficiently opened to admit all our fingers, we turn the back of our hand to the fundament, while our thumb and fingers being flattened, flide along between the head and rumpbone, ufing fometimes the right, fometimes the left-hand.'

In oppofition to which, from reafon and experience, we declare the forceps can never be profitably employed till the head is very low down in the pelvis, and seldom till it begins to push out the perinæum backwards; in which fituation every practitioner knows there is no room for the hand to be paffed up, and even turned round between the head of the child and the end of the rump-bone.

The third and laft part treats of diseases of the mother before delivery, after delivery, and of thofe of infants; which is methodical, concife, and feems to be judiciously drawn up.

We are extremely forry our duty to the public has obliged us to be fo fevere on Dr. Memis: however, he has, for the most part, carefully abridged what he found in different authors; and we make no doubt that after twenty years practice. and experience, he will be able to publish a complete treatise on the subject of midwifery.

VI. Excerpta Quædam e Newtoni Principiis Philofophia Naturalis, cum Notis variorum. 4to. Pr. 10s. 6d. Nourse.

IT

T is the bufinefs of those who adhere to the prefent method of philofophifing, established by Sir Ifaac Newton, to find out the laws of nature by experiments and obfervations, and derive the caufes of all things from the moft fimple principles poffible. Philofophers of this kind will frame no hypothefis, nor receive them into philofophy otherwife than as questions whose truth may be difputed; they proceed therefore in a two-fold method, fynthetical and analytical. From fome fele&t phonomena they deduce, by analyfis, the forces of nature, and the more fimple laws of forces; and from thence, by fynthefis, fhew the conftitution of the reft. To this, with a proper application of geometry, is owing the great advantage the present fyftem of philofophy has over all the preceding ones, and the vaft improvements it has received within the last age. What wonderful advancement in the knowledge of nature may be made by this method of enquiry, when conducted by a genius equal to the work, will be best underfood, by confidering the discoveries of the illuftrious philofopher above-mentioned. To him it is principally owing that we have now a rational system of natural philofophy, who, by pursuing the fure and unerring method of reafoning from experiments and obfervations, joined

with the most profound skill in geometry, has extended his enquiries to the most minute and invisible parts of matter, as well as to the largest and most remote bodies in the universe; and who has enablished a fyftem, free from the uncertainty of a mere hypothefis, raised upon the fecure and lafting basis of geometry itself.

As the philofophy of Newton is now univerfally received, it is our opinion that a well executed treatise tending to elucidate the more difficult parts thereof, cannot fail of being acceptable to fuch as are defirous of being acquainted with the true fyftem of the world, which, in fome meafure, feems confirmed by the encouragement given to the work now before us, by fo large a number of fubfcribers.

Our author, after premifing the neceffary definitions, enumerating the laws of motion, and clearly explaining the feveral corollaries that flow from thofe laws, divides the remaining part of the work into fix fections. In the firft of thefe, Sir Ifaac Newton's method of prime and ultimate ratios, together with the lemmas that compofe the first fection of the first book of the Principia, are treated by the learned editor in a manner fuitable to the importance of the subject.

Section 2. The invention of centripetal forces, the 38th, 39th, and 40th propofitions in the firft book of the Principia, are here illuftrated with great judgment and propriety.

Sect. 3. treats of the motion of bodies in eccentric conic fections. Here the reader will find the 11th, 12th, 13th, 14th, 15th, and 16th propofitions of the first book of the Principia explained in a curious and fatisfactory manner.

Sect. 4. In this fection, previous to the investigations relating to the attractive forces of spherical bodies, our learned author propofes and demonftrates the following useful theorem ;

Quantitates materiæ in corporibus funependulis, quorum centra oscillationum a centro fufpenfionis æqualiter diftant, funt in ratione compofitâ ex ratione ponderum et ratione duplicatâ temporum ofcillationum in vacuo.

DEM. Nam velocitas, quam data vis in datâ materia, dato tempore generare poteft, eft ut vis et tempus directè, et materia inverfè. Quo major eft vis, vel majus tempus, vel minor materia, eo major, generabitur velocitas. Id quod per motus la gem fecundam manifeftum eft. Jam vero fi pendula ejufdem fint longitudinis, vires motrices in locis a perpendiculo æqualiter diftantibus funt ut pondera: ideoque fi corpora duo ofcillando describant arcus æquales et arcus illi dividantur in partes æquales ; cum tempora quibus corpora defcribunt fingulas arcuum partes correfpondentes fint ut tempora ofcillationum totárum erunt velocitates ad invicem in correfpondentibus ofcilla

tionum

tionum partibus, ut vires motrices et tota ofcillationum tempora dire&è, et quantitates materiæ reciprocè; ideofque quantitates materiæ ut vires et ofcillationum tempora dire&tè et velocitates reciprocè. Sed velocitates reciprocè funt ut tempora; atque ideo tempora directè et velocitates reciprocè funt ut quadrata temporum; et propterea quantitates materiæ funt ut vires motrices, et quadrata temporum, id eft, ut pondera et quadrata temporum. Q E. D.

Cor. Ideoque fi tempora fint æqualia, quantitates materiæ in fingulis corporibus erunt ut pondera.'

Notwithstanding this demonftration is very concife and elegant, we apprehend it might have been rendered more easy to be understood by the generality of readers by an analytical procefs, as thus: Let F and ƒ represent the motive forces, T and the times employed by thofe forces to generate the velocities. V and in the quantities of matter M and m refpectively. It is well known that V:v:: FxTfxt. Multiply extremes and

M

ገነ

means, we have V xƒxt×M=vxFxTxm; whence M: m :: FxTxv:fxtxV; or M: m :: but V: v::t: T,

FXT.fxt
V

and : T : tT; therefore V xt: vxT: : t2: T2: from hence we get:::T: 2, and confequently M : m :: F×T2: jxt. Q. E. D.

ข

Cor. If Tt, then M: m :: F: f.

In the remaining part of this fe&tion our author has greatly facilitated the investigations of the 70th, 71st, 72nd, 73, 74th, 75th, 76th, and 78th propofitions in the first book of the Principia; and, as a fpecimen of his truly understanding the doctrine of ultimate ratios, we fhall make the following extract:

Si quantitates duæ a+x et b+y componantur ex partibus datis a et b, et ex partibus non datis, fimul tamen nafcentibus, vel fimul evanefcentibus, x et y; fuerit autem a+x ut b+7; erit femper x ad y ut a ad b. DEM. Cum enim ponatur a+x ut by, erit femper a+x ad b+y in datâ ratione; nafcentibus autem vel evanefcentibus x et y, est a+x ad b+y, ut a ad b; quare axerit femper ad b+y, ut a ad b; ideoque x erit ad y femper ut a ad b.

Aliter, Eft a+x:b+y:m:n ex hypothefi: fit et ỷ cotemporanea finita incrementa vel decrementa x et y, et erit a+ x + x = b+y+j:: m n ex hypothefi; ergo a+x+x: b+y+j::a+x: b+j, et ab + bx+bx+ay+yx+yx=ab+ ay+aj + bx+xy+xy, et bx+y=aj+xy; atque idcirco : ja+xb+ym: n. Si vero cotemporanea incrementa vel decrementa quantitatum duarum, quæ fimul exiftere incipiunt, femper vel æquales fint vel in eâdem ratione, quantitates ipfæ vel æquales erunt, vel in hâc ratione; hoc eft, erit

*