September 12, 1895] 



NATURE 



459 



I 



"indefinite wall," which is characterised by the fact that 

 temperature differences in the parallel jManes are exactly pro- 

 portional to the distances of these planes. According to the 

 experiment, they get the result that this proportionality does 

 not exist, and that conductihility varies much according to 

 temperature. 



In my opinion, this absence of proportionality arrived at, 

 proves rather that the experimental conditions were defective, 

 and are in contradiction with the hypothesis of the " indefinite 

 wall " case. 



I admit, in principle, the employed method, but I think it 

 should be modified until — for the same temperature of the latli, 

 the said proportionality should be obtained ; then, in a new 

 exiwriment. the temperature of the bath being higher, it should 

 lie verified if the proportionality and the conductihility remain, 

 or if the last increases or diminishes with the temperature. 



Neuchatel, August. Robert Weber. 



Experimental Mountain-building. 



Prof. Johannes Walther, of Jena, requests me to com- 

 municate to you the following details regarding an interesting 

 experiment which he has recently devised for teaching purposes : 

 it is intended to explain mountain-formation. 



He compares the system of folds on the surface of our slowly- 

 ageing earth to the wrinkles which form on the skin of a drj-ing 

 apple, and points out that the height of our mountain-chains in 

 relation to the mass of the globe is precisely comparable to the 

 wrinkles on the skin of the apple. In order to demonstrate the 

 formation of these folds, he takes an indiarubber balloon (a), 

 and attaches to it a bit of glass tubing (B). On to this is 

 stretched a piece of indiarubber tubing (c), which is pinched 

 close by the stopcock (i>). When the indiarubber balloon is 

 blown out to its full capacity, it is spread over with a layer of 

 flour-paste two millimetres thick, and is then dipped and 



twirled round and round in dry wheaten flour until a per- 

 fectly smooth crust, three to four millimetres in thickness, covers 

 the whole sphere. The balloon is then placed on a tripod, so 

 that the indiarubber tubing (c) dips exactly into a glass of 

 water standing below. Thereupon the stopcock is turned open, 

 and the air is allowed to escape in single bubbles : the volume 

 of the ball is lessened, and lateral pressure makes itself immedi- 

 ately felt in the paste-crust. Small folds gradually grow bigger, 

 single fiilds unite to form systems of folds, flat areas of depres- 

 sion sink deeper and deeper, and the neighbouring folds twirl 

 and cross over the depression. The features of the Cordilleras, 

 of the Jura, and many other well-known tectonic relations are 

 thus reproduced with striking accuracy. Whenever it is desired 

 to repeat the experiment, one need simply blow the balloon out 

 again, smooth out the folded surface by dipping and twirling in 

 dry flour, and all is ready for another demonstration. 



London, August 26. L. Belinfante. 



Joseph Thomson. 



In Mr. Gregorj-'s sympathetic notice (Nature, p. 440) of 

 Joseph Thomson, he hardly docs justice to the memory of the 

 deceased traveller in relation to the scientific results of his ex- 

 jieditions ; at least so far as botany is concerned. During his 

 too short career Thomson presented three considerable col- 

 lections of dried plants to Kew. The first, which appears to 



have been made on his own initiative, chiefly between Lake- 

 Nyassa and Lake Tanganyika, was secured for Kew in 1880, 

 through the instrumentality of the late Colonel J. A. Grant, 

 F.R..S. This was not the subject of a special paper: yet it 

 contained a number of interesting novelties, some of which 

 have from time to time been published in Hooker's '" Icones- 

 Plantarum '' and elsewhere. Before going out j^ain Thomson 

 carefully studied the means by which his collecting opportunities 

 might be turned to the greatest advantage, .\rmed with this 

 knowledge he collected even more successfully in the Kilimanjaro' 

 and other mountains of Eastern Equatorial .\frica. This second 

 collection reached Kew in September 1884, and proved of the 

 greatest scientific importance, being the first adequate illustra- 

 tion of the mountain flora of that region. It contained scarcely 

 150 species ; but the specimens were selected with admirable 

 judgment, and were sufficient for all jiurposes. It was worked 

 out by Sir Joseph D. Hooker and Prof D. Oliver, and the very 

 important results recorded in the twenty-first volume of the 

 fotinial of the Linnean Society. This paper and Thomson's 

 collection will always rank among the classical documents for the 

 study of the phytogeography of Central Africa. Subsequently 

 Mr. Thomson sent to Kew the botanical fruits of his journey to 

 the Atlas Mountains, and although they contained very few 

 previously unknown plants, they were none the less instructive 

 as a sample of the flora of that comparatively little-known part 

 of the world. Had he preserved his health Thomson might 

 have taken his place in the first rank of botanical explorers. He 

 had ac(|uired the rare gift of selection in collecting ; of knowing, 

 what to secure and what to neglect. 



W. BOTTING HeMSLEV. 



Late Nestlings. 



To-D.\v I observed nests of the house-martin underneath the 

 eaves of the clock-tower at Lamlash Pier, on the south and west 

 sides. The parents were busy feeding their young, whose cries I 

 heard. Surely this is a late date for a migratory bird. How. 

 are these nestlings to get across the ocean ? Jas. Shaw. 



Barrhead, September 7. 



THE INSTITUTE OF FRANCE. 



IN a few weeks, at the end of October, the Institut 

 National de France is to celebrate its first cen- 

 tenary. Some words concerning its origin and organi- 

 sation may be of interest at the present moment. 



The Institute is the outcome of a previous scientific 

 society, entirely due to individual initiative. During the 

 first half of the seventeenth century, a few men, between, 

 whom love of science was a firm bond, agreed to meet at 

 regular intervals at the house of one of their number, in- 

 formally, in order to exchange views, to keep each other 

 posted up on their various researches, and to make up an 

 unconventional assembly of congenial spirits. It was 

 more of a temporary or intermittent club than a real 

 society, as we understand the latter now. These men 

 were mostly mathematicians and physicists — for at that 

 time natural science was more in the •u'crdcn than 

 in the scitt state — and Mersenne, Descartes, Blaise Pascal, 

 Gassendi, are some of them. Their meetings soon 

 attracted public attention, and the great Colbert, anxious 

 for the development of the arts of peace after the Pyrenees 

 treaty had put an end to the war, considered them as 

 being of sufficient importance and utility to take an 

 interest in them, and to support the incipient society 

 officially. 



Colbert even made out a full plan of what was to be 

 realised 200 years later ; what he organised was a body 

 of scientific men who were to meet at regular inten-als> 

 and were divided into three classes — historical scholars, 

 literary men, and, finally, scientific men. The private 

 society of mathematicians and physicists grew into the 

 Academic des Sciences, and each of the three academies 

 met separately in the Bibliotheque du Roi, at Colbert's 

 own residence. The king, as a sign of his approval, 

 gave some money for experiments, and some pensions. 



NO. 1350, VOL. 52] 



