Oct. 4. 1883 J 



NATURE 



539 



recent of the electrical inventions, Mr. Mumo has tried 

 to accomplish a well nigh impossible task. That he 

 should have been perfectly successful in his endeavour is 

 hardly to be expected ; nevertheless he has produced a 

 book which a person unacquainted with electrical science 

 may read with pleasure, and from which such a person 

 may learn what wonders are accomplished by the aid of 

 electricity, and in a general way how this powerful and 

 subtle agent does its work. 



The first thirty-one pages, in which the author gives so 

 much of the theory of electricity as may be necessary to 

 enable any one to understand his descriptions of the 

 inventions which follow, form without doubt the weak 

 part of this book. In describing the effect of grouping 

 thermopiles and elements in series, the author seems to 

 have confused electromotive force with current strength, 

 for he says that with such a combination a powerful 

 current equal to the sum of the elementary ones will cir- 

 culate in the connecting wire. The short chapter on 

 induction is likely to cause in the mind of a person unac- 

 quainted with electrical science some confusion between 

 statical and current induction. 



With the fourth chapter a description of the inventions 

 begins, and here it may be said that the book proper 

 begins. The chapters on the telegraph and telephone 

 and all the inventions which depend on the telephone are 

 excellent, the general principles being so clearly given as 

 to be readily understood. The theory of the dynamo is 

 too difficult for an essentially popular book, and here, as 

 in one or two other places, the author has wisely refrained 

 from leading his readers into a sea of complexity from 

 which they could with difficulty have escaped, but has 

 carried them over with an agility worthy of a conjurer. 

 The remaining chapters, which deal with lighting, trans- 

 mission of power, heating, and plating, are written in a 

 popular style, and will no doubt be read with interest. 



C. V. B. 



LETTERS TO THE EDITOR 



[The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts, 

 No notice is taken of anonymous communications. 



[ The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible otherwise to insure the appearance even 

 of communications containing interesting and novel /acts.] 



Professor Henrici's Address at Southport 



Mr. J. J. Walker, in his letter printed in your last number 

 (p. 5 : 5)> draws attention to the works of Chasles, and I am glad 

 that he has thus given Hie an opportunity of saying a few words 

 about the relation in which the writings of this great geometer 

 stand to those of the German geometers mentioned in my 

 address. 



I am fully aware that his works are well known in England, 

 and so I believe are th ise of Poncelet and others. But the 

 study of the works of Chasles does not give as complete a view 

 of the variety of methods invented and results obtained on the 

 Continent as might be expected from the author of the " Apercu 

 Historique" (1837). In that brilliant work he regrets himself 

 that he does not understand German, and does not therefore give 

 an account of what was done in Germany by " Steiner, PJiicker, 

 Mobius, &c," and it seems that he always remained ignorant of 

 it. At all events he did not fill up those gaps in his imp riant 

 "Rapport "of 1870. In much of his own work contained in 

 his " Apercu " he had been anticipated by Mobius and Steiner, 

 and his "Geometrie Superieure," which appeared twenty years 

 later than Steiner's " Entwickelungen," and twenty-six years 

 later than the " Barycentrische Calcul," by Mobius, and which 

 is, I believe, in England considered the chief book from which 

 to learn modern C ntinental geometry, must not be taken as a 

 standard of what at the time of its publication was known in 

 Germany. 



With regard to the arithmetic, I beg to point out that I only 

 judge from my experience as an examiner. The methods of 



abbreviating calculations with decimals must have been known 

 long before De Morgan, I fancy, but that is a very different thing 

 from having them introduced as an important part of the teach- 

 ing of arithmetic in schools. 



Juanner in which a large number of candidates worked 

 examples at the London University Matriculation Examination 

 slartled me considerably, especially as I noticed that the process 

 of working decimals described in my address was used by candi- 

 dates who otherwise gave evidence of really sound knowledge 

 and good teaching. O. HENRIC1 



The New Comet 



The new comet (Pons) was seen here last night in the 6-inch 

 equatorial, its place closely corresponding to that of the 

 ephemeris contained in the recent Dun Edit Circular. 



In the comet eyepiece it was large, round, and faint, with no 

 tail and but little trace of central condensation. It might, in 

 sw eeping have been taken for a nebula, having very much that 

 look. I could not see it in the 2-inch finder, and though fairly 

 visible in the comet eyepiece (power 35), a very little mist that 

 came up rapidly obscured it. J. Hand Capron 



Guildown Observatory, Guildford, October 2 



The Genus " Simotes " of Snakes 



In the report of the Committee appointed by the British 

 Association for the investigation of Timor Laut, given in at 

 Southport during the recent meeting, I find that among the 

 snake-, discovered by me one has been described as a new species 

 of Simotes, and is noted as being of 'Special interest, as no 

 species of the genus had hitherto been previously known to 

 occur eastward of Java." In the Proceedings of the Zoological 

 Society for the year 1864, p. 180, a species of Simotes, S. aus- 

 tralis, was described by Gerard Krefft, from Port Curtis, 

 Australia, as being "the first Simotes discovered in Australia." 



Aberdeen, October 1 Henry O. Forbes 



Floating Pumice 



Referring to a note in the last number of Nature (p. 532), 

 giving an account of a steamer's having encountered vast 

 quantities of pumice in the Indian Ocean, it may be of interest 

 to record that after passing, in the R. M.S. Quetta, the Straits of 

 Sunda on July 9 last (having sailed close under the then active 

 Krakatoa), we traversed a continuous field, unbroken as far as 

 the eye could reach, of pumice, every day till the evening of the 

 12th, when our position must have been six hours (± 60 miles) 

 to the west of our noon position, 93° 54' E. long, and 5° 53' S. 

 lat. Capt. Templeton assured me that there was, singularly 

 enough a current against us all the way from the Straits of 

 one-third of a mile pet hour. There can be no doubt 

 that this pumice came from Krakatoa, and possibly also that 

 mentioned by the steamer in your note last week. The pumice 

 knobs were all water-worn, and a few had barnacles of about 

 one inch in length growdng on them. It will be recollected that 

 the eruption first broke out on May 22 and 23. 



Aberdeen, October 1 Henry O. Forbes 



" Elevation and Subsidence " 



In the number of Nature for September 20, Mr. W. F. Stanley 

 (p. 488) requests references to where it has been considered that 

 the sinking on the coast of Greenland is due to the weight of 

 inland accumulation of ice. If Mr. Stanley has only so lately 

 as the present year advocated this opinion, though doubtless the 

 idea has arisen independently with him, he certainly has no right 

 to consider himself the originator of it, which he seems disposed 

 to do. So far as I am aware the priority is due to Mr. T. F. 

 Jamieson (Quart, fount. Geol. Soc. vol. xxi. 1865), who attri- 

 buted the subsidence, which is universally conceded to have 

 occurred during the Glacial period, to the enormou- weight of 

 snow resting on the land, considering that if the interior of the 

 earth on which the crust rests is in a state of fusion, a depression 

 might take place from a cause of this kind ; and then the 

 melting of the ice would account for the rising of the land which 

 seems to have followed upon the retreat of the glaciers. 



Unaware of this proposition, in 1871 (President's Address, 

 Five. Liverpool Geol. Soc. 1871-72 ; Geol. Mag. vol. ix. 1872) I 

 in the same way ascribed the subsidence of the land during the 

 Glacial period to the combined weight of snow and the boulder 



