598 



NATURE 



{Oct. 20, i! 



(comparatively spealiiiig)defccnding currents may very likely, as 

 it appears to me, be the cause of these appearances. Now just 

 as at the surface of the earth these minor currents of convection 

 are continually jjoiug on, and mixing up the heated portions lielow 

 with less heated portions above, till at last a great catastrophe 

 takes place, and we have a thunderstorm or even a cyclone ; so 

 the same thing may take place at the surface of the sun, and 

 minor currents of convection may gradually cause a coohng of a 

 gi-eater stratum, and at last the equilibrium becomes unstable, 

 and a great change takes place between the superficial portions 

 and those v\hich lie beneath, and we have the manifestations of 

 faculse and spots. According to this view the faculse would 

 consist of the heated portions on a larger scale coming from the 

 interior, and the spots of a subsequent down-rush on a large 

 scale of the portions which had been erupted and had cooled by 

 radiation. Kirchhoff supposed that the spots were due, not to de- 

 pressions of the sun, but to clouds of comparatively cool gases or 

 vapours rising above the general surface. This was in contradiction 

 to the relative altitudes of ihe sun-spots and the general surface 

 as made out originally by Wilson, and subsequently confirmed 

 by the observations of others ; and moreover there are some other 

 difificnUies connected VI iih it. Let us suppose that there is an 

 eruptio'.i of hydrogen which has got cool, then if that exists and 

 there is a cold draught at some distance above the sun, we cannot 

 say it would absorb any longer the rays which it is capable of 

 absorbing when glowing, because the correspondence of en ission 

 and absorption only necessarily holds good on condition that the 

 substance is at a given temperature. If the temperature changes 

 it is possible, and in many cases we know it is a fact, that the 

 mode of absorption may change with it. We know that the 

 cold hydro;;en is transparent ; we know, theoretically at any 

 rate, that glowing h)drogen must be opaque with regard to light 

 of the particular refrangibility which it emits ; hence a cool 

 mass of gas might cease to be opaque even by virtue of its being 

 cooled. Again, if we had a cloud of, say, vapour of iron, and if 

 this were condensed into actual drops or globules of molten iron 

 in the upper portinn of the atmosphere, they would form such a 

 very rare sort of mist as would be something lilvc a very rare 

 haze which barely obscures the sun, and would not give rise to 

 more than a slight general darkening. But if the gases in 

 descending got warmed attain, they would then be in a condition 

 to absorb light specifically ; but being at a lower temperature 

 than the sun they would not give out nearly so much light as 

 they absorb. 



That seems to me to be the most natural explanation of the 

 spots and of the phenomena attending them. I may have some- 

 thing more to say about this on a future occasion ; but, as I see 

 the time is going on, it w ould probalily be more agreeable to you 

 that I should postpone anything further I have to say to you 

 upon this subject uutil my next lecture, in the course of which I 

 hope, as I have said, to point out a speculation as to the connec- 

 tion which exists between sun-spots and certain pihenomena 

 which we know exist at the surface of the earth. There are 

 probabilities to my mind in favour of it, but I will, with your 

 permission, defer allusion to it to my next lecture. 

 {To be continued.) 



THE HELVETIC SOCIETY OF NATURAL 

 SCIENCES 

 T^HIS Society held its sixty -fourth annual session at Aarau on 

 August 8, 9, and 10, under presidency of Prof. Muhlberg, 

 whose opening discourse treated of recent progress in physiology 

 and chemistry. An account of the proceedings (of which we 

 here offer a brief resumi) will be found in the Archives des 

 Sciences. 



In the Section of Physics and Chemistiy Prof. Forel read a 

 valuable paper on the periodic variations of glaciers. These 

 periods of advance and retreat are proved to embrace several 

 years (five to twenty and more) ; they are due in the first instance 

 mainly to variatnn in velocity of the glacier, and this to small 

 variations in the th ckiiess of the nhii repeated in the same 

 sense for several >ears, ihe con equent variation of velocity be- 

 coming much m ire pro ouncrd as the glacier descends, and the 

 ultimate effect bei g se araied by matiy years from its original 

 cau-e. 'Ihe varwiig heat ol :uinmt-r appeu'S to be of quite 

 secondary imporiH me In one of three papers, communicated 

 by M. kaoul Piciei, he descrilieil tii new mcihod of ditiUaton 

 and rectification of sjnriis by a raiio"al use of low temperatures. 



The two processes are performed at once ; and with considerable 

 economy a purer product is obtained. Another pape; explained 

 the principle of his rapid steamer, now being made, and the 

 working of which will be watched with interest. The third 

 treated of the different qualities of steel as regards magnetisation 

 and permanence of magnetic powei. (To this and the pre- 

 ceding, reference has been already made in our columns.) 



M. Krippendorff exhibited a model of a balloon, to be pro- 

 pelled in light winds by escape of compressed air at the end of a 

 wooden axis rendered horizontal or inclined according to the 

 direction aimed at (by shifring the suspension of the car). The 

 air would be compressed by four men into a small copper re- 

 ceiver at the other end of the axis ; and a second reservoir 

 holding liquid carbonic acid would be at band in case of need. 

 In a micro-telephone described by Prof. Amsler-Laffon, the 

 flame of a manometric cap'ule (like those of Konig) is inserted 

 in a telephone circuit; iis conductivity being increased with 

 vapi'Urs of 1 otassium. Its change in form and size through 

 vibrations of a thin jlate of steel under sound, entails changes in 

 electric resistance, and the telephone is affected acordingly. 

 The apparatus is said to be very sensitive. Some useful hints 

 on representation by projection of longitudinal and transversal 

 vilirations are given in a paper by Dr. R. Weber. MM. Soret 

 and Sarasin indicated a new method of determining the angle of 

 rotation of quartz, and showed, in a curve, how the rotatory 

 power vaiies with the wave length. 



An interesting observation is reported by Prof. Dufour, who 

 finds in deformation of images produced on large surfaces of 

 calm water, a new proof of the roundness of the earth. This 

 may often be witnessed on the Lake of Geneva, e.g. Ihe reflected 

 steeple of Montreux, seen from Merges ; and in the case of ships 

 some kilometres distant at sea. Prof. Forel, from a study of 

 the recent earthquakes in the Cantons of Vaud and Neuchatel, 

 finds analogies to the phenomena of a vibrating plate in Chladni's 

 experiments ; the intensity and direction of a shock, e.g. being 

 very different in places quite near each other. Guided by theo- 

 retical considerations, M. Chappuis has measured the liberation 

 of heat through condensation when water is introduced suddenly 

 into an evacuated tube filled with charcoal in temperature equi- 

 librium with the w ater, and from the data, and the compres-iliility 

 of water he infers the adherent w ater to be under a pressure of 

 at least 36 million atmospheres. Among other subjects discussed 

 were the measurement of radiant heat with the differential ther- 

 mometer (Dufour), the determination of tartar and tartaric acid 

 in wines of commerce (Piccard), and the action of bromine on a 

 mixture of water and sulphide of carbon (Ureck). 



In Zoology M. Fatio gave some account of his continued re- 

 searches on disinfection with sulphurous acid. The vapours act 

 in two ways on all organisms which depend on oxygen for life, 

 viz. asphyxiating them by suppression of that element, and 

 gradually burning them interiorly, the acid being dissolved in 

 their humours or aqueous parts ; the doses and times of appli- 

 cation are varied accordingly. The more aqueous in substance 

 an animal or plant is, the more quickly is it affected. The dose 

 and time of application, in different receivers, will also be varied 

 according to the temperature affecting diffusion of gas and the 

 hygrometric state of the air and enveloping material. M. Fatio 

 operated successfully on vibrions and bacteria in infusions sub- 

 mitted to an atmosphere mixed with sulphurous acid (the depth 

 of the liquid here determines the time of exposure), and the 

 range of application is evidently wide. M. Vogt gave some 

 interesting facts showing the extensive adaptation of colours in 

 animals of the Saharan Desert to that of the ground. With 

 regard to the exceptional colour of nearly all Coleoptera, viz. 

 black, he considers they find protection in their bad smell, and 

 also their strong resemblance, when contracted and feigning 

 death, to excrement of gazelles, goats, and sheep. The animals 

 brought to the surface by water of Artesian wells in that region 

 M. Vogt finds to be quite without the characters of animals living 

 in caverns and subteiranean water; their eyes are well deve- 

 loped, and their colours pronounced. They are indeed proved 

 to live but temporarily underground. With albuminised paper 

 Prof. Forel fixed 40 metres as the limit of penetration of chemical 

 rays into water, but Dr. Aspen has, by a different method, got a 

 photographic effect in the Lake of Zurich as far down as 90 

 metres. The researches of I'r. Yung on the influence of food 

 on fi-'ig development have been formerly noticed ; and of the 

 remaining sulijects we merely niite the sense of colour in Cepha- 

 lopoda (Keller), a peculiar m.ide of copulation in dci drocoele 

 marine worms (Lang), and the conditions of production of 



