July I, iSSo] 



NATURE 



199 



near Bayeux, on the 31st of May, 1S80. His name is 

 honourably associated with experimental researches in a 

 good many of the less-frequented bye-paths of electrical 

 science. Living in a time which may well be regarded 

 as the transition period, during which electricity has 

 passed from the stage of a phenomenal and experimental 

 science to one of exact mathematical relations, some of 

 Gaugain's investigations are already superseded by the 

 later and more comprehensive researches of a younger 

 generation. Yet he has done good work, which will live 

 to carry down his name along with that of Peltier, of 

 Pouillet, and of Becquerel, and with the still greater 

 names of Arago and of Ampfere. 



His earliest contribution to science of which we are aware 

 was a memoir published in 1S53, under the title "Note 

 5ur les Signes Electriques attribuees au Mouvement de 

 la Chaleur," and in the same year he brought out his 

 tangent galvanometer. The essential point of this instru- 

 ment consisted in employing as a coil several turns of 

 ■wire of increasing diameter arranged about a conical sur- 

 face, at whose imaginary apex was placed the small mag- 

 netic needle, each of the coils thus subtending the same 

 solid angle at this point. This arrangement, to which 

 ■Gaugain w-as experimentally led, was in some points 

 virtually anticipated by the tangent galvanometer of 

 Helmholtz, in which, however, a symmetrical arrange- 

 ment was employed. In the same year Gaugain announced 

 the discovery that continuous currents of electricity could 

 be produced by the continuous friction of two dissimilar 

 metals upon one another. The ne.\t two years saw him 

 employed in investigating the electricity produced by 

 evaporation and by combustion. In 1856 he produced 

 his double-condenser electroscope, designed, like the con- 

 densing-electroscope of Volta, for the investigation of the 

 electrification due to contact of dissimilar substances. At 

 the same time he published some observations on the be- 

 haviour of amalgams of sundry metals, and showed that 

 in a voltaic pair the amalgam of zinc was more electro- 

 positive than zinc itself, while the amalgam of cadmium 

 was on the other hand, more electro-negative than the 

 pure metal. From 1856 to 1859 Gaugain was occupied 

 with important inquiries on pyroelectricity, and he suc- 

 ceeded in establishing sundry law-s, with respect to the 

 electricity of the tourmaline in particular, which had 

 escaped previous observers. The results he arrived at were 

 published in the A miah-s dc Chiiiiie ct de Physique, and com- 

 prised a number of curious and une.xpected results. The 

 tourmaline, which at ordinary temperatures is a bad con- 

 ductor, evenforhigh-tcnsion electricity, begins to conduct at 

 4oo°0r5oo°C., and on cooling is stillfoundto conduct; but if 

 washed in water and dried carefully it once more insulates. 

 All tounnalines are not equally active, those of Brazil, 

 green or blue in colour, being the most electrical. In 

 order to obtain a measure of the amount of electricity 

 furnished by a tourmaline whose poles were united by a 

 metallic circuit, he devised a discharging gold-leaf electro- 

 scope, and by means of this instrument showed that a 

 number of tourmalines united by their similar poles gave 

 quantities of electricity proportional to their number, 

 while if united in single series they gave no more than a 

 single long one, thus behaving like batteries of great 

 electromotive force and of almost infinite internal resist- 

 ance. The quantities of electricity furnished by tourma- 

 lines of equal lengths but of different thickness while 

 passing through equal ranges of temperature he found to 

 be proportional to the cross-sections of the crystals, again 

 agreeing with the law of Ohm as applied to batteries of 

 very high internal resistance. Gaugain also showed the 

 quantity of electricity thus flowing through the tourmaline 

 in one direction during a rise of temperature to be equal 

 to that flowing in the reverse direction during a corre- 

 sponding fall. The year following the discharging 

 electroscope was usefully employed in verifying Ohm's 

 law as applied to other bad conductors. Volta's contact 



theory occupied Gaugain at several periods of his career, 

 and he established amongst other interesting results that 

 there is a difference of potential between a piece of 

 platinum which has been dipped into acid, and one which 

 has been dipped into alkali, even though both have been 

 subsequently washed. Gaugain also conducted a number 

 of careful researches on specific inductive capacity, on 

 the capacity of cables, on the residual charge of con- 

 densers, and on what he termed the variable electric 

 state of a condenser communicating with the soil by a 

 bad conductor, in which, when discharged by disruptive 

 sparks or by the discharging electroscope, the time- 

 intervals of the discharges were found to form a geometric 

 progression. His extended observations on condensers 

 of spherical, cylindrical, and flat forms were communi- 

 cated to the Academic des Sciences in three special notes. 

 In later years Gaugain devoted himself to the examina- 

 tion of the effects of heat upon the magnetism of steel 

 tubes and bars, and found the remarkable result that a 

 bar magnetised powerfully while hot may when cooled 

 exhibit a reversed polarity, and vice versa j also that the 

 magnetisation by a strong current penetrates deeper than 

 that due to a weaker current. He also brought to light 

 sundry analogies between the behaviour of magnets under 

 magnetic force, and of matter generally under mechanical 

 forces. 



Born in Normandy in 18 10, he entered the Ecole 

 Polytechnique at about the age of eighteen, and after- 

 wards attended the Ecole d'Artillerie at Metz, after which 

 he adopted metallurgy as his profession. Gaugain worked 

 during the closing years of his life in isolation and in 

 straitened circumstances, assisted by his only daughter, 

 who devoted herself to him. His researches, though 

 several times rewarded with academic recognition, were 

 not in themselves productive of gain ; and the prix Cegner, 

 an annual grant of 4,000 francs, given a tin savant paiivre 

 afin de Vaidcr dans ses recherclies, awarded to him for 

 five years past, was a welcome amelioration of _ his 

 position in a time of failing health and during the painful 

 illness to which he succumbed at the age of seventy 

 vears. S. P. T. 



A CHAPTER IN THE HISTORY OF THE 

 CONIFER.E 



IN working out the Eocene coniferas, in continuance of 

 the monograph which the Pateontographical Society 

 are kindly publishing and illustrating in a sumptuous 

 manner, some reflections upon the past history of the 

 more prominent Eocene genera, such as Araucaria, Podo- 

 carpus, Dammara, Sequoia, &c., have occurred to me, 

 which, although being perhaps outside the scope of the 

 Palxontographical So:;iety's work, may not be uninterest- 

 ing to the general readers of Nature. I have therefore 

 tentatively brought forward the present chapter on Arau- 

 carias without yet having any definite intention of putting 

 together my notes upon the other genera, in the present 

 form. 



^r(7?/<ra;/(j:,^ Jussieu.— The earliest traces of distmctly 

 coniferous wood known, those from the Carboniferous, 

 were for many years thought to belong exclusively to 

 the Araucarian type. This supposed prototype became, 

 according to Schimper, modified in successive ages, and 

 he endeavours to trace these modifications through the 

 extinct genera Walchia, Ullmannia, Araucarites, Voltzia, 

 Pcycholepis, Pachyphyllum, and Cunninghamites. Les- 

 quereux, however, carries the actual genus Araucaria 

 to as far back as the Trias, and unmistakable cones 

 of both sections of the genus have been described by 

 Carruthers from the Stonesfield, Yorkshire, and Somer- 

 setshire oolites ; fossil forms agreeing closely with these 

 have been also found in the Jurassic of India. It is not 



' From Araucanos, a peiple cf Chili, in which country A. imbrkata. 

 abounds, and furnishes the principal food of the Indians. 



