Jan. 31, 1878] 



NATURE 



26 



Wolf during eighty years before 1787 give io"23 years (or, 

 if we take nine cycles, io'43 years) for the mean duration. 

 It is by mixirg these two very different means that the 

 Zurich astronomer finds ii'i years, a mean that can evi- 

 dently have no weight given to it. On the other hand, if 

 Dr. Wolf is in error (as I believe he is) as to the existence 

 of a maximum in 1797, the mean durations for the 

 eighty years after, aad for the eighty years before 1787 

 agree as nearly as the accuracy of the determinations for 

 the beginning of the eighteenth century will admit. 



I beg, then, to repeat that since the time when regular 

 series of magnetic observations were commenced, till new, 

 there is no difference whatever between Dr. Wolf and 

 the magneticians as to the synchronism of the two 

 phenomena. 



Under these circumstances we come to the question — 

 Are the sun-spot maxima and minima really synchronous 

 with those of the magnetic diurnal oscillations ? I have 

 already said that this was so in 1787 ; and, considering 

 only the cases for which we have complete materials for 

 comparison, beginning with Schwabe's observations of 

 sun-spots, it was so for the maxima of 1829, 1837, 1848, 

 i860, and 1870, and for the minima of 1824, 1833-4 (q. p.), 

 1844, 1856, 1866, and it is the case for the minimum at the 

 present time. These coincidences are far more im- 

 portant, as showing a common cause, than may appear at 

 first sight from this summary. 



The successive oscillations of the sun-spot variations 

 are not performed in equal times, neither are those 

 of the magnetic variations. Was the duration of the 

 oscillation for the sun-spots only eight years, as from 

 the maximum in 1829 to that of 1837, so was that 

 for the magnetic variations ; did it amount to 12^ 

 years nearly, for the sun-spots, as from the minimum 

 of 1844 to that of 1856, this was also the case for 

 the oscillations of the needle. Does the sun-spot 

 variation proceed from a minimum to a maximum within 

 about three and a half years as from 1833-4 to 1837, so 

 does the magnetic oscillation. Does the sun-spot varia- 

 tion occupy nearly eight years between a maximum and 

 the following minimum, as from 1848 to 1856, so does the 

 diurnal oscillation of the needle. 



It will be difficult to persuade physicists that, during 

 nearly a century the sun spot cycle has been shortened or 

 lengthened, and the sun-spot variations have been accele- 

 rated or retarded, so nearly together with those of the 

 diurnal oscillations of the magnet, by accidental coinci- 

 dences. No doubt the admission of the existence of a 

 causal connection between the two phenomena is opposed 

 to the hypothesis, which many other facts render now 

 wholly untenable, that the magnetic variations are due to 

 the heating action of the sun. 



I am obliged to Prof. Piazzi Smyth for giving me the 

 occasion to explain a difficulty which has troubled others 

 as well as himself. John Allan Broun 



January 23 



HENRI VICTOR REGNAULT 



THE death of M. Becquerel, alluded to in our last 

 issue, was followed on the 19th inst. by that of his 

 friend and fellow-physicist, M. Regnault, whose name is 

 associated so intimately with the elementary principles 

 of our knowledge of heat. Henri Victor Regnault was 

 born at Aix-la-Chapelle, July 21, 1810. His youth was 

 spent in a hard battle against poverty in the effort to 

 maintain not only himself^ but his sister. While still a 

 lad he wandered to Paris, and there obtained a position 

 as assistant in the large drapery establishment known as 

 Le Grand Coude, a name familiar at the present day to 

 the lady visitors of Paris. Here ability and fidelity won 

 for him friends, and at the age of twenty he was enabled 

 to gratify his longings for a scientific education, and enter 

 the 6cole Polytechnique of Paris, the Alma Mater of so 

 many famous French savants. After a course of two 



yeais here, in 1832 he entered upon active duties in the 

 department of mines, and was absent from Paris for the 

 next eight years. During the latter portion of this time 

 he occupied a professor's chair at Lyons, and had a 

 laboratory at his disposal. Here he embraced the oppor- 

 tunity to enter upon the field of research in organic 

 chemistry, which had just sprung into existence as a 

 branch of chemical science, under the hands of Liebig, 

 Wohler, Laurent, Dumas, and others. While many of 

 the chemists of the day were engaged in theoretical 

 disputes, and the battle between the electro-chemical 

 theory and the newly-advocated type-theory was being 

 hotly waged, Regnault devoted himself to the accu- 

 mulation of the facts so sorely needed as founda- 

 tion-stones by the disputants on both sides. Among 

 his investigations at this time may be mentioned those 

 on the composition of meconine, piperine, canthari- 

 dine, and other alkaloids, composition of pectic acid, 

 identity of esquisetic acid with maleic acid, proper- 

 ties of naphthaline-sulpho-acid, &c. By the action of 

 sulphuric anhydride on ethylene, he obtained the carbyl- 

 sulphate, C2H4S20g, which Magnus prepared later from 

 alcohol. His most valuable researches, however, were on 

 the halogen derivatives in the ethyl-group, especially 

 interesting at the time of their appearance, when the 

 theories of substitution were timidly being advocated. 

 Among these compounds now familiar reagents to the 

 organic chemists were mono-chloro-ethylene-chloride, 

 CH2CI.CHCI2, obtained by the action of chlorine on 

 ethylene chloride, as well as the higher chlorinated 

 derivatives, which offered one of the most striking 

 instances of substitution. These were followed shortly 

 after (1838) by the classical investigations on the actions 

 of chlorine on ethyl- chloride C2H5CI, in which one by one 

 all of the hydrogen atoms were successively substituted 

 by chlorine, until the limit, CaClg was reached. Of im- 

 portance also was the change of ether, C4H10O, into 

 perchloroether, C4CI10O. Another interesting series of 

 preparations gave the substituted ethylenes by the action 

 of alkalies on saturated halogen derivatives, ethylene- 

 bromide for example, yielding vinyl-bromide, and hydro- 

 bromic acid : — 



CaH^Brg + HKO = CgHgBr -f KBr + HgO. 



By this method he discovered vinyl-bromide, vinyl-iodide, 

 vinyl-chloride, dichlor- ethylene, C2H2CI2, and trichlor- ethy- 

 lene, C2HCI3. Finally must be mentioned his discovery of 

 carbon tetrachloride, CCI4, by leading chlorine into boiling 

 chloroform. It is difficult for us at the present day to 

 estimate the importance attached to these discoveries 

 forty years ago, when every new fact was a glimmer of 

 light to the organic chemist wandering in the dark, and 

 few series of researches have stood the test of time so 

 well as those carried out by Regnault in his Lyons labo- 

 ratory. The faithful study of minute properties, and the 

 careful attention to physical peculiarities, already gave 

 evidence of the tendencies which were manifested more 

 fully in another branch of science, and the appearance of 

 his papers in the Annales de Chiviie et Physique attracted 

 the attention of the scientific world to the hitherto un- 

 known provincial professor. In 1840 he was elected to 

 replace Robiquet in the chemical section of the French 

 Academy, and was appointed professor in the Ecole 

 Polytechnique. In the following year he was elected to 

 the chair of physics at the College de France. A few 

 years later he became engineer-in-chief of mines, and in 

 1850 received the order of officer in the Legion of 

 Honour. 



With his removal to Paris the field of Regnault's inves- 

 tigations was changed. Like our own Faraday, after 

 having obtained renown as a chemist, he suddenly turned 

 physicist. He was scarcely established in Paris, when 

 he began his famous series of experiments on specific 

 heat. A few years previous, Dulong and Petit had deter- 

 mined the specific heat of a number of elements by 



