Oct. 17, 1S73 



NATURE 



503 



supply a want that lias been felt for some lime past, and the new 

 society is one that ought to succeed, and, if properly managed, 

 will be sure to l)e of immense service in the Bombay Presidency. 



We learn from the Garden that the directors of the Alexan- 

 dra Park Company have requested Mr. M'Kenzie to prepare a 

 sclieme for establisliing a school of horticulture, for which 

 purpose al)Out twenty acres of the grounds attached to the 

 building will be set apart. As we have no school of horticul- 

 ture in this great gardening country, we hope something more 

 may come of tliis than of its short-lii'ed and feeble forerunners. 



The Porluguese yornal de Horliailltira Pratica announces 

 a forthcoming "Flora" of that countrj', by Seiior Barao de 

 Castello de Piava, who was formerly Professor of Botany in 

 the Acidemia Polylhenica. Great things are expected from the 

 new work, in which the subject will be brought up to the 

 level of the knowledge of the present day, including all tlie 

 discoveries which have been made since the time of Brotero, 

 whose onre celebrated "Flora Lusitanica" is now seldom to 

 be met with for sale. 



A NEW Revue des Seieiiees Naturellcs has recently been started 

 at Montpellier under the management of MM. Dubreuil and 

 Keeker, to be published every three months. 



We learn that the publication of the American yournal of 

 Conchchigy has closed with the completion of its seventh volume. 

 This quarterly, edited by Mr. George W. Tryon, has appeared 

 under tiie auspices of the Academy of Natural Sciences hi 

 Philadelphia, and has included, from time to time, a great many 

 very important conchological monographs, chiefly presented to 

 the Philadelphia Academy, many of them accompanied by 

 coloured plates. Hereafter, such communications will be pub- 

 lished in the Journal of the Proceedings of the Academy itself. 



The Second part of the Qiiart,rh' Go-man Magazine, just 

 received, contains translations (still into very indifferent English) 

 of only two articles: Dr. J. Rosenthal on Electric Phenomena, 

 and Prof, de Bary on Mildew and Fermentation. 



Les Moiides has a long description, with illustrations, of the 

 new " Horloges electriques" of M. C. F. Milde, the principal 

 of which is a commutator for distributing the hours in all direc- 

 tiors. It consists of an electromagnet proportioned to the 

 requirements, whose armature, at the moment of attraction, acts 

 upon the arm of a lever, which governs a sector, whose centre 

 of rotation is upon a pillar. 



An apparatus has been recently devised in Germany for ob- 

 taining specimens of water at any desired depth of the ocean. 

 A strong, heav>' vessel, entirely closed and empty, has a valve 

 through w'hich water may be admitted, but which is only put 

 in motion by means of powerful electro-magnets connected 

 therewith. These magnets are also connected with a wire which 

 accompanies the rope, by means of which the apparatus is lowered 

 from the ship. When the empty vessel, which is in fact a 

 plvimmet, has reached the required depth, an electric current is 

 sent from the battery on shipboard to the coils below ; the mag- 

 netism thus generated opens the valves, and the vessel is filled 

 and ready to be drawn up. 



According to the correspondence of the N'eto York Herald, 

 an ingenious plan has been adopted by Prof. Agassiz's expedition 

 for determining how far the submarine regions are pervious to 

 lijht. A plate prepared for photographic purposes is inclosed 

 in a case so contrived as to be covered by a revolving lid in the 

 space of forty minutes. The apparatus is sunk to the required 

 depth, and at the expiration of the period stated is drawn up and 

 c^evclopcd in the ordinary way. It is said that evidence has 

 thus been obtained of the operation of the actinic rays at much 

 gicatcr c'cpllis than hitherto supposed possible. 



THE BIRTH OF CHEMISTRY 

 II. 

 Thales of li/iletus — Later Icliefs in his doctrine —Anaximencs — 

 Empedokles — ITerakleitos — Anaxagoras — Demokritos — The 

 Atomic Iheory — Aristotle — The Ethereal Medium — Trans- 

 mutation of the Elements — The Four-element Theory — Mode 

 of interpreting it — Cause of the ahence of Natural Science 

 among the Ancients. 

 npiTE elements of the Greek philosophers were, as we shall pre- 

 -*■ sently show, ra\httr principles than elements in the sense in 

 whichw-e speak of the sixty-five elements now known to chemistry. 

 There was a marked tendency in the earliest period of Greek 

 philosophy to make one element or principle fundamental, and 

 to evolve the other elements and the world from it. Thales, of 

 Miletus, who lived in ihe sixth centur)', B.C., and who was 

 called "the first of natural philosophers'' by TertuUian, and the 

 "first who inquired after natural causes" by Lactantius, 

 affirmed that water was the first principle of things, perhaps, 

 according to some writers, because Homer had made Okeanos 

 the source of the gods. At least we are reminded of the bound- 

 less w-ateiy chaos of older cosmogonies. This doctrine of Thales 

 was not without its supporters during the Middle Ages, and, 

 indeed, the convertibility of water into earth and air was not 

 absolutely disproved until about a century ago. One of the 

 ablest sujjporters of the dorn-.a was Van Helmont (b. 1577, d, 

 1644), who affirmed that al rr.: tals, and even rocks, may be re- 

 solved into water ; animal substances are produced from it, be- 

 cause fish live upon it ; and vegetable substances may be also 

 produced from it. This last assertion he endeavoured to prove by 

 what would appear to be a very conclusive experiment in those 

 da)s, when neither the composition of the air nor of water was 

 known. He took a willow which weighed five pounds, and 

 planted it in two hundred pounds of earth, which he had pre- 

 viously carefully dried in an oven. The willow was frequently 

 watered, and at the end of five years he pulled it up and found 

 that its weight amoun'ed to one hundred and sixty-nine pounds 

 and three ounces. The earth was again dried, and was found to 

 have lost only two ounces. Thus it appeai-ed that 1641b. of 

 wood, bark, roots, leaves, &c. , had been produced from water 

 alone. Hence he inferred that all vegetables are produced from 

 water alone ; not knowing, as was afterwards proved by Priest- 

 ley, that a constituent of the atmosphere called carbonic acid 

 had furnished the solid part of the tree, although, indeed, 

 there was much water with it. Boerhaave devotes a page 

 of his big book to a discussion of "whether water be 

 convertible into earth." He concludes that the small earthy 

 deposit observed when rain-water is distilled, arises from the 

 particles of dust which had settled on the water before its intro- 

 duction into the distilling vessel. Mr. Boyle h.ad previously 

 affirmed that " a very ingenious person, who had tried various 

 experiments on rain-Hater, put him beyond all doubt about this 

 transmutation, for he solemnly affirmed, on experience, that rain- 

 water, even after distillation in very clean glasses, near two 

 hundred times, afforded him this white earth." Finally, Lavoi- 

 sier, in 1770, communicated to the Academic des Sciences an 

 elaborate paper, "On the nature of water, and the experiments 

 by which it has been attempted to prove the possibility of 

 changing it into earth." In this he conclusively proved that 

 water cannot be changed into earth, although it be distilled 

 backwards and forwards for many successive days. Here then 

 we find the old Thalesian theory at last disproved, but not before 

 it had endured for twenty-four centuries ; and this is by no mears 

 a solitary example of the permanence of old ideas. We shall 

 become acquainted with yet older theories, which are still ad- 

 mitted, and which seem to be essential to physical philosophy. 



On the other hand, Anaxinienes regarded air as the primal 

 element, Plerakleitos fire, Pherekides earth, and some philosophers 

 grouped two elements together. Anaximenes held that clouds 

 were caused by the condensation of air, rain by the condensation 

 of clouds ; he appears to have clearly connected condensation 

 with cold, rarefaction with heat. Archelaus affirmed that air 

 when rarefied becomes fire, vhen condensed, water. It was very 

 generally believed during the Middle Ages that water when 

 boiled was converted into air. Empcdokles introduced the idea 

 of four distinct elements — earth, air, fire, and water, not capable 

 of passing one into the other, but forming all things by their 

 intermixture. These elements are acted upon by two principles, 

 a uniting force of amit}', a rcparat'ug force of discord, corre- 



