346 



NATURE 



Feb. lo, 1 88 1 



may pass through the sensitised paper, the resistance R 

 must be high ; the e m f of the battery b must therefore 

 be great, and several cells should be used. 



An electromotive force is produced by the action of the 

 platinum point, and the metal cylinder upon the sensi- 

 tised paper, and the resulting current is for many reasons 

 very annoying. I have got rid of this by coating the 

 surface of the cylinder with platinum foil. 



Stains are apt to appear upon the under-surface of the 

 paper, which sometimes penetrate through and spoil the 

 picture. They may be prevented by washing the surface 

 of- the cylinder occasionally with a solution of ammonia. 



Slow rotation is essential in order both that the decom- 

 position may be properly effected and that the selenium 

 may have time to change its resistance. The photophone 

 shows that some alteration takes place almost instan- 

 taneously with a v.T-iation of the light, but for the greater 

 part of the change a very appreciable period of time is 

 required. 



The distance between the two instruments might be a 

 hundred miles or more, one of the wires, M, n, being 

 replaced by the earth, and for practical use the two cylinders 

 would be driven by clockwork, synchronised by an electro- 

 magnetic arrangement. For experimental purposes it is 

 sufficient to connect the two spindles by a kind of Hooke's 

 joint (some part of which must be an insulator), and drive 

 one of them with a winch-handle. 



The instrument might be greatly improved by the use 

 of two, four, or six similar selenium cells and a corre- 

 sponding number of points. If two such cells were used 

 the transmitting cylinder would have two holes, diametri- 

 cally opposite to each other, with a selenium cell behind 

 each. A second point would press upon the under surface 

 of the receiving cylinder, and be so adjusted that the 

 lines traced by it would come inidway between those 

 traced by the upper point. Four or six selenium cells 

 could be similarly used. The a:ijacent lines of the picture 

 might thus be made absolutely to touch each other, and 

 moreover the screw upon the spindles might be coarser, 

 which for obvious reasons would be advantageous. A 

 self-acting switch or commutator in each instrument 

 would render additional line-wirei unnecessary. 



Shelford Bidwell 



NOTES 



The Murohiion medal of the Geological Society has this year 

 been awarded to Prof. Geikie. 



The Associateship of the Institute of Chemistry, along with 

 the prize of 50/., offered by Prof. Frankland for the "best 

 research involving gas analysis," has been awarded to Mr. Frank 

 Hatton, of 14, Titchfield Terrace, Regent's Park, student in the 

 Royal School of Mines, South Kensington. 



We regi-et to record the death, at the age of seventy-seven 

 year.s, of Mr. John Gould, F.R.S., the eminent ornithologist. 

 We hope to give some account of his life .ind work in our next 

 number. 



A REMARKABLE discovery has been made by Mr. Alex. 

 Adams, one of the technical officers of the Post Office Telegraph 

 Department. It is the existence of electric tides in telegraph 

 circuits. By long-continued and cireful observations he has 

 determined distinct variations of strength in those earth currents, 

 which are invariably present on all telegraphic wires, following 

 the different diurnal positions of the moon with respect to the 

 earth. lie will read a paper on the subject at the meeting of 

 the Society of Telegraph Engineers to-night. 



Mr. Joseph Thomson has, we understand, received the offer 

 of an advantageous post under the Sultan of Zanzibar, which no 

 doubt he is likely to accept. Mr. Thomson's work will be 

 mainly that of geological surveying in the region of the Rovuma 

 River, and the Sultan has offered him every facility for carrying 



on the work. The Sultan deserves every credit for showing such 

 enterprise, and we have no doubt that Mr. Thomson will be able 

 to do work of great scientific value. 



At the Royal College of Surgeons Prof. W. K. Parker, 

 F.R.S., will give nine lectures on the Structure of the 

 Skeleton in the Sauropsida, on Mondays, Wednesdays, and 

 Fridays, February 11, 16, 18, 21, and 23, at 4 p.m. Prof. 

 W. H. Flower, LL.D., F.R.S., will give nine lectures on 

 the Anatomy, Physiology, and Zoology of the Cetacea, on 

 Mondays, Wednesdays, and Fridays, February 28, March 2, 

 4. 7. 9. II. 14. 16, and iS, at the same hour. 



We are glad to learn that the new 23-inch object-glass of 

 Prof. C. A. Young of Princeton, N.J., is completed. Prof. 

 Young has tested it at Cambridge, Mass., and finds it very fine"; 

 he hopes by and by to do some good stellar spectroscopic work 

 with it. The mounting is well under way, and it is expected 

 that the instrument will be in place next autumn. 



Mr. Lamont Young, the Government geologist of New 

 South Wales, has suddenly and mysteriously disappeared, and 

 foul play is suspected. Mr. Young arrived safely at Bermagui, 

 iSo miles south of Sydney, and at once set out to cross the bay 

 in a boat. No news of him came in, and tw-o days later his boat 

 was found jammed among the rocks of the coast, ten miles north 

 of the point from which he had started. It was at fir»t, and 

 naturally, supposed that Mr. Young and his company had been 

 drowned, and that his boat had drifted on shore. A closer 

 examination proved that the boat had been drawn carefully up 

 on the coast, and that the party had dined after landing. Next 

 some bullet holes were found in the boat, and this suggested the 

 idea that the explorers had been attacked and murdered. But 

 not a single mark of blood or additional trace of any violent 

 assault could be discovered. The party were five in number, 

 and the coast has been examined for traces or tidings of them in 

 vain. An official of the Mines Department has been assisted by 

 detectives and by the boasted "black trackers," natives whose 

 acuteness is seldom at fault in a case of this sort. 



Prof. McK. Hughes writes on Jannuary 27, suggesting 

 the following scientific uses of the late severe weather : — • 

 When this frost breaks up and the frozen snow and ice 

 begin to travel along our rivers to the sea there will be an 

 opportunity of making observations upon several points upon 

 which accurate information will be of use in seeking an expla- 

 nation of some of the glacial and post-glacial phenomena of the 

 British Isles, e.g. (i) Dimensions of the icefloes; (2) whether 

 they consist chiefly of frozen snow or solid ice, i.e. an approxi- 

 mate estimate of their specific gravity; (3) amount of material 

 carried by them and dimensions of larger boulders ; (4) whether 

 any of these were dropped on to the flje from cliffs of glacial 

 drift so as to give scratched stones and remanie drift in modern 

 mud ; (5) how far out to sea such floes have been traced with or 

 without earth and stones ; (6) salinity of the water where the 

 observations were made; (7) transport of shore shells, &c., by 

 ice ; (8) crumpling of mud by impinging ice ; (9) grinding of ice 

 along bridge piers, and many similar observations which it will 

 be useful to record. 



The great annual soirk at the Observatory of Paris has been 

 a greac success. Almost all the Cabinet ministers and M. 

 Gambetta were present. A plan was exhibited in the Astro- 

 nomical Museum showing the present state of the Observatory, 

 and what it will be when all the works for which credits have 

 been voted shall be completed. A ball took place after a series 

 of lectures and projections given in the graiiJe galerie. One of 

 the lecturers, M. Berlus, exhibited magic mirrors, and reminded 

 those present that in 1S44 M. Mouchez, then a junior officer in 

 the French naval service, brought home with him one of these 

 mirrors from Japan, which was presented to the Academy 



