Ocl. 2 1, 1880] 



NATURE 



585 



no bearing on the subject of the high temperatures obtained by 

 breathing through woven material on the bulb of a thermometer, 

 for no one has yet observed that woollen clothing will develop a 

 heat greater than that of the body it covers, viz., 98° '5. 



The hygroscopic properties of difTerent materials afford no 

 explanation of the phenomena, for the power of materials to im- 

 bibe moisture will not account for an increase of their tempera- 

 ture by breathing through them. 



My speculations may be right or wrong ; Mr. McNally has not 

 shown them to be either. My facts are not the less true from 

 being incompatible with "ascertained physiological truths," for 

 ascertained physiological truths are only true so long as they are 

 not controverted by other ascertained physiological truths. 



My experiments show that the temperature obtained by breath- 

 ing on the thermometer in the manner described is higher when 

 less caloric is abstracted from the surface of the body, lower 

 when the surface of the body is losing more caloric. Thus on a 

 warm summer day my breath raised the thermometer to 108°, 

 whereas to-day (a cold wet day) it only raised the thermometer 

 up to 103". Does not this seem to show that respiration is a 

 means of getting rid of the superfluous caloric generated in the 

 body, and that when this excess of caloric cannot be got rid of 

 by the skin it passes off by the breath ? R. E. Dudgeon 



October 9 



Selenium 



As the only chance of being able to transmit images of 

 reflection through a conducting wire, in the way sound is 

 repeated to a distance by telephone, appears to lie in the 

 preparation of a fairly transparent sheet of metallic selenium ; 

 it may tend to advance the subject if the difficulties experienced 

 in dealing with this substance are mentioned. 



Selenium in its vitreoua condition melts about 220° Fahrenheit, 

 and can be drawn out between mica plates over a lamp, to a 

 thin transparent red film. But heated for some time it turns 

 black and granular, apparently absorbing hydrogen, then melts 

 only at 423° F., and is brittle and intractable. Unfortunately 

 it is only in this crystalline state that its power of conducting 

 electricity appears, and varies with the light under v.'hich the 

 selenium is placed. 



Prepared in the mass, electrically conducting se'enium is as 

 compact as the hardest gas carbon, with the shiny appearance 

 and surface of graphite. How to reduce such a substance to 

 any degree of transparency is perplexing. By reducing it to 

 fine powder, and subjecting the black selenium to severe hydraulic 

 pressure between hot poU^hed steel plates, thi desired eflfect 

 might be produced. Selenium also dissolves freely in chloride 

 of selenium, Se2Cl2, and precipitates slowly in a botyroidal mass 

 of black selenium. It also separates in the crystalline form 

 from concenti'ated solutions of selenide of potassium or sodium. 



There is some uncertainty as to whether a transparent sheet 

 could be more easily obtained by the method of precipitation, 

 than by mere mechanical treatment. But the investigation is 

 one that requires to be carried out with the aid of a fully 

 equipped laboratory, and is beyond the power of an ordinary 

 experimentalist. 



To de\-ise a successful mode of making a black substance like 

 graphite at all translucent, requires a distinct understanding of 

 the reason why bodies are opaque. Something more than an 

 explanation in general terms is needed before camera pictures 

 can be resolved into electric currents, and again integrated upon 

 a receiving plate. 



Perhaps some of the readers of Nature may be able to 

 suggest a method of dealing with selenium that will produce 

 thin transparent sheets capable of conducting electricity. 



London, October 16 A. T. F. 



Dynastes Hercules 

 The reviewer of Ober's "Camps in the Caribbees " (Nature, 

 vol. xxii. p. 216) appears to doubt the story of the habits of the 

 Large Hercules beetle, Dynastes hcnulcs, given by Ober on the 

 authority of his guide. It is nevertheless perfectly true, and I have 

 myself w itnessed the occurrence twice in this neighbourhood, where 

 the beetle is not uncommon. In the first instance I noticed it on a 

 branch of Ochroma la^opus, and the «econd time on a species of 

 Bombax, both very soft-wooded trees. The branches in each 

 case were about three-quarters of an inch in diameter, half an 

 inch being formed by the wood. In both cases I saw the per- 

 formance of the animal most distinctly, just as described by 



Ober's guide, and I took not only a piece of the severed branch 

 with me, but secured also the second animal. The noise is not 

 so much produced by the cutting of the branch as by the open 

 wings passing rapidly through the air during the rotation of the 

 beetle. I do not believe there is anything of a sexual call in the 

 manceuvre. The beetle wints to get at the abundant juice of the 

 young branches. It is called in this country aserrador, i.e. 

 sa-i-nyer. Golofa porteti, an allied insect of the same family as 

 Lamellicornes, behaves in a similar way, but chooses, of course 

 thinner branches. A. Ernst 



Caracas September g 



What is Alrese ? 



In the large Encydopedie published by Diderot and d' Alembert, 

 vol. xii. p. 224 (edit, in folio) there is mentioned amongst the 

 substances used for poisoning water to catch the fish, I'herbe qii'on 

 appelk /'alrese. Littre has no such word, nor anything like 

 it, nor indeed any other lexicographer I am able to consult here. 

 I should be much obliged for any information on this name, or 

 the plant referred to. A. Eenst 



Caracas, September 9 



Rainfall of Sierra Leone 



As I believe there is little account taken of this climate at 

 home, and as perhaps it might interest you, I send you an account 

 of one day's rainfall this month, which is an excessive amount 

 even for Freetown, and equal to one-third the whole year's 

 rainfall for Dublin, I believe : — 



Rainfall registered in the Colonial Hospital, Freetown, ^o feet 

 above Sea-level 



Inches. 



From 6 a.m. to 4 p.m. September 1 1 6'35 



From 4 p.m. to 6 a.m. September 12 4*05 



Total in 24 hours 

 Garrison House, Freetown, 

 September 16 



io'4 



W. Hume Hart, 

 Colonial Surgeon 



An Octopus 



I INCLOSE an account of an enormous octopus which was 

 thrown on the shore at Kilkee, Co. Clare, in the last great storm. 

 As strangers find my uncle's hand very hard to read, I have 

 copied his letter. 



Ardanoir Foynes C. G. O'Brien 



" Saturday, October % 1880 



" I am sorry you were not at Kilkee when a great octopus was 

 stranded on the side of the Duggerna reef on Thursday last. 

 Its arms had been partially broken : there were eight of them, 

 cacli as thick as a strong man's upper arm, and beneath each 

 were two rows of suckers like cupping-glasses, more than a 

 shilling size in circuit. When perfect, each of the^e arms must 

 have been from twelve to fifteen feet long, and from the point of 

 one arm to that of its opposite was a length of nearly thirty feet. 

 The animal's length from the insertion of its suckers to the end 

 of its body must have been nearly twenty feet, perhaps more. 

 Its, mouth, like a parrot's beak, was as large as two joined hands 

 of a large man with the fingers outstretched. It weighed about 

 4 cwt. Its head was \\ inch in diameter, abuut three feet long ; 

 its eyes of the size of the inner circuit of a breakfast-plate. A 

 monster. The under colour that of tlie under side of a turbot." 

 —{From a letter of the Rev. R. T. Gabbett.) 



A^ 



SYNTHESIS OF CITRIC ACID 

 S we intimated last week, another brilliant synthesis 

 ■ has lecently been accomplished in the domain of 

 organic chemistry. Messrs. Grimaux and Adam have 

 succeeded in building up the characteristic acid of lemons 

 from glycerin. Glycerin may be regarded as trihydroxy- 

 propane, C,H5(OH)3, and citric acid as hydroxypropane- 

 tricarboxyliic acid, C,Hi(0 H)(C0.,H)3. To convert glycerm 

 into citric acid it was therefore necessary to replace two 

 hydroxyl groups, and one hydrogen atom, by the group 

 C'O.H (carboxyl). This was done as follows :— By the 

 action of hvdrochloric acid on glycerin, dichlorhydrin. 



