riety of fubjects, or to give our readers any notion of what they may expect to find in thefe volumes, we fhall only felect from different parts of the work a few paffages, fo as to convey fome idea both of the author and tranflator's manner.

Of the Vine Fretter,

You have frequently feen little flies fastened in great num-. ber to the upper extremities and leaves of plants, and twist them round in various forms: thefe are vine-fretters, whofe fpecies are almoft as numerous as those of vegetables, and whose remarkable properties are multiplied in proportion to the attention we pay them. They bring forth living young ones. Their births are eafy to trace, there needs only good, eyes and a little patience. Take up a little one as foon as it is produced; inclofe it immediately in the most perfect folitude, and in order to be the better affured of its virginity, carry your precautions to a degree of fcrupuloufnefs; be with respect to it a more vigilant Argus than the fabulous one. When the little reclufe has acquired a certain growth, it will begin to have young, and after fome days, you will find it amidst a numerous family. Make the fame experiment on one of the individuals that you have tried on its chiefs the new hermit will multiply like its father, and this fecond generation, brought up, in folitude, will not prove lefs fruitful; than the first. Repeat. the experiment from one generation to another; abate nothing of your cares, your precautions, your fufpicions; proceed, if your patience will permit you, to the ninth generation, and they will all prefent you with fecund virgins, After these experiments fo decifive and reiterated, you are eafily perfuaded that there is no diftinction of sex in vine-fretters. What indeed would be the ufe of fuch a difference among a people, where all the individuals are conftantly fufficient for themselves? Natural history is the beft, logic, because it beft teaches us to fufpend our judgment. Vine-fretters are really diftinguished by fexes, and their amours are the least equivocal of any in the world. I do not know whether there are in nature any males more amorous than they. What then is the ufe of coupling between infects that multiply without its affiftance? Of what fervice can an actual diftinction of fex be to real androgynes. The clearing up of this point depends on another fingularity afforded us by thefe little animals. During the fummer feafon they are viviparous they all bring forth living young. Towards the middle of autumn they become oviparous; they all then lay real eggs, which are hatched at the return of fpring. The males begin to appear exactly at the time the females begin to lay. There are always found in the bodies of the females,

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males, eggs and young ready to be produced.

The young

then were originally inclosed in eggs. During the fine season they are hatched in the belly of the mother, and are brought into the world alive. Plants at that time furnish them with proper nourishment. The developement depends ultimately on nutrition: vine-fretters that are produced alive, are more unfolded in the matrix than those which are brought forth inclosed in eggs. The former then have received a nourishment in the matrix. Had not coupling, then, for its primary end, the supplying the defect of this nourishment in fuch germs as were not to be hatched till after they had iffued from the belly of the mother?'

We shall next tranfcribe the chapter upon ants, as it may tend to remove an almost universal mistaken opinion of fome thousand years standing, concerning the forefight and provident induftry of thofe infects.

How aftonishing muft the activity of thefe laborious in- fects be, by which they are enabled to collect the materials neceffary for the construction of their neft! Behold their fagacity in uniting together, and affifting each other in fcooping out the earth, in order to tranfport to their habitation bits of herbs, ftraw, fcraps of wood, and other bodies of the like kind, which they employ in their work. They feem only to pile it up in heaps at random; but under this apparent confufion is couched art and defign, which is perceived upon a fecret examination. Under this little heap, of which their lodging confifts, and whofe form facilitates the paffage of the water, are discovered galleries, which communicate with each other, refembling the streets of a little city. We are particnlarly ftruck with the folicitude of ants for their nurflings, with the care they take to convey them in proper time from one place to another, their nourishing them, and caufing them to fhun every thing that may prove hurtful to them. not but admire the readiness with which they withdraw from danger, and the courage they fhew in defending them. An ant has been seen, after being cut asunder in the middle, to tranfport eight or ten of its nurflings, one after another. They feek their provifions at a great diftance from their abode. Various paths, which are often very winding and intricate, terminate at their neft. The ants pafs over them in rows, without ever miffing their way, any more than the republican caterpillars. Like the latter they leave tracts wherever they pafs. These are not difcernible to the eye; they, are much more fenfible to the finell; and it is well known that ants have a very penetrating one. However, if we draw a finger feveral times backward and forward along the wall, by which

One can

the

the ants pafs and repass up and down in rows, they will be ftopped on a fudden in their march, and it will afford fome amufement to obferve the perplexity they are in.

The forefight of ants has been greatly celebrated. Near three thousand years ago it was remarked, that they amaffed provifions for the winter; and were fkilful in building inagazines for containing the grain they had collected during the fine feason. It would feem that thefe magazines must be altogether ufelefs to them, infomuch as they fleep during the whole winter, like dormice, and many other animals. A fmall degree of cold would be fufficient to benumb them. We may conclude thence that they have no ufe for these pretended magazines; and confequently do not build them. The corn they convey with fo much activity to their dwelling, is by no means intended by them for food; but confifts only in fimple materials, which contribute to the construction of their edifice, in the fame manner as little bits of wood, ftraw, &c.'

This extract, we apprehend, will be fufficient to give our readers an idea of the author's manner of treating his subject. The book is not to be confidered as a system of natural hiftory, but as containing a great variety of curious facts, most of which may be found difperfed in other authors. Monfieur C Bonnet himself informs us in his preface, that we are to confider this work as a kind of abridgment of, or introduction to, his other writings; and that it is in fact nothing more than a fuperficial furvey of nature. As to the tranflation, we cannot poffibly pronounce it elegant. The ftile is frequently poor, and the fentences injudiciously turned; and yet, upon the whole, many of our tranflators from the French write worfe English.

V. The Elements of Clock and Watch-work, adapted to Practice. In two Effays. By Alexander Cumming, Member of the Phil. Soc. Edinb. 4to. Pr. 155. Millar. [Concluded]

IN

N our Review for laft month, we gave a fpecimen of this performance, fo far as relates to the improvement of clocks without increase of expence: we now come to the improvement of fuch clocks as are intended for the most accurate purposes.

Here the author. begins with an examination of fuch means as have heretofore been used for diminishing friction and the influences of the oil: he feems not to approve the ufe of friction pullies; and fays, that the method ufed by Mr. Huygens of having his marine clocks wound up every half minute, may be of some small advantage in clocks that remain in their place,

but

but of none in portable machines of whatever construction. He next defcribes the operation and nature of pallets he had feen with Mr. John Harrison, and Mr. Hindley of York, in "neither of which the ufe of oil was neceffary; but though he allows this contrivance to be very ingenious, he fays, that the performance with fuch pallets can never be perfect, owing to the number of springs; and the recoil, that are infeparable from this conftruction. He expatiates warmly in favour of the dead beat; that in practice it has hitherto been loaded with difadvantages; that a fair comparative trial would evince its fuperiority to the recoiling principle; and gives feveral reasons why no trial hitherto made could be decisive.—This enquiry into the nature of pallets appears to us very ingenious and useful; but however true the conclufions, experiment must bring the Arongeft conviction in matters fo very intricate and little cultivated.

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Mr. Cumming next defcribes a conftruction of pallets, with which the theory and practice of the dead-beat will exactly correfpond. Thefe pallets are of a very ingenious construction, and we believe them ufeful: the following note we infert for the curious. Such pallets I finished in the year 1763, for a CLOCK which I had the honour of making for the king; for journalizing all the changes that happen in the height of the mercury in the barometer, which it does in fuch a manner, that a perfon who has not feen a barometer for the whole year, may, by infpecting its dial, know with the greateft cafe and certainty, not only what changes have happened on any day of the year; but alfo, every one change that exceeds the hundredth of an inch, which happens in the whole year, with the day and hour, as well as the particular manner in which each did happen.".

Our author concludes the improvement of clock movements with the defcription of a conftruction of pallets yet more perfect, the properties of which we fhall give in his own words"Thefe pallets correct all the irregularities of action in the mainfpring, wheels and pinions, or any other irregularities that can poffibly happen in the movement, from any cause whatever; though the causes of fuch irregularities fhould altogether escape the attention of the artificer He confiders no further improvement in clock movements neceffary; fhews, that any motion of the point of fufpenfion 'Will alter the natural times of vibration of a pendulum, more than if its length had undergone án alteration equal to the face defcribed by the point of sufpenfion; and how this evil may be avoided he reduces all the contrivances that have been used for correcting the effects of heat and cold, on the pendulum rod, to two classes; and fhews that all fuch thermometers as belong to the one of those claffes,

muft

muft ever have an imperfect effect; that in fome cafes, wooden pendulum rods may be advantageoufly applied, and that the performance of the clock may be hurt, by wholly correcting the effects of heat and cold on the pendulum rod that the mercurial pendulum must ever be too quick in its effect; that fquare bars of metal, clofely fitted together; or hollow cilinders; can never have a perfect effect that the gridiron pendulum and Mr. Ellicott's is fuperior to any other contrivance yet produced for this purpose; and that by removing fome imperfections in the prefent conftruction of Mr. Ellicott's, it may be rendered fuperior to any that has yet appeared, and equal to any that can be produced.

Mr. Cumming, laftly, enquires into the effects that any change of denfity in the air, would have on the times of vibration of clock pendulums; which fubject he introduces thus" Having fhown above, how to render the maintaining power perfectly uniform; the point of fufpenfion immoveable and the length of the pendulum invariable; fuch changes as happen in the denfity of the air, feem now the only remaining caufe that can alter the length or time of vibration."-In treating this matter, he obferves, that any change of denfity in the air, has two feparate effects on pendulous vibrations, the one arifing from its weight independent of its refiftance; the other, from the refiftance independent of the weight: that the former only, affects the times of vibration in the cycloid; but that both take effect and correct each other in circular arcs.'- -Though we are not fully fatisfied, that thofe two effects of the air do in circular arcs exactly ballance each other, we doubt not, that in the cafe here stated they render fuch vibrations as are performed in the arc of a circle, preferable to those performed in the cycloid, or in any other curve yet investigated.

On the whole: we meet with more ingenious remarks and matter of improvement in this first effay, than could reasonably have been expected in an art fo long practifed by men whose great genius, knowledge, and abilities, have juftly rendered this kingdom famous for the many accurate performances of this nature it has produced. We muft alfo do the author the justice to say, that his manner of treating the fubject, and his competitors for fame, fhows a degree of candour oftener to be wifhed for than met with; and though we could with for the fatisfaction of the curious, as well as for the fake of improvement, that theeveral articles here treated were confirmed by experiment we cannot deny the truth of what he fays in the end of his conclufion to this effay, "But prudence forbids an attempt that requires fo much time, expence, and application.”

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