I 



Nov. 14, 1889] 



NATURE 



47 



blocks, which, on relief of the tension by escape of lava or 

 vapour, are readjusted by gravity, in new positions. The blocks 

 may be rectangular in section, but are more likely to be rhom- 

 boidal or wedge-shaped ; giving level tables with fault cliffs (as 

 in the plateau region) in the one case, and tilted blocks with 

 normal faults (as in the basin region) in the other. The author 

 considers the Sierra and Wahsatch to have been formed by 

 lateral crushing and folding ; and the region between to have 

 been arched, broken, and readjusted, as described, in the end of 

 the Tertiary. — Two determinations of the ratio of the electro- 

 magnetic to the electrostatic unit arefurnished from the Johns Hop- 

 kins University ; one made this year, by Mr. Rosa, by Maxwell's 

 method of measuring a resistance, the other ten years ago, by 

 Messrs. Rowland, Hall, and Fletcher, by measuring a quantity 

 of electricity electrostatically, and then measuring it electro- 

 magnetically with a galvanometer. The former gives v = 

 2*9993 X lo^" centimetres per second ; the latter, 2'98i5 x 10^" 

 centimetres. It seems certain, according to Mr. Rosa, that v is 

 within a tenth per cent, of 300 million metres per second. — M r 

 Long continues his account of the circular polarization of certain 

 tartrate solutions ; and his experiments point to a law that the 

 rotation of a double tartrate may be made to approach that of a 

 neutral tartrate of either of the metals present, by addition of a 

 salt of that metal (the effects being apparently explained by 

 substitution). — Mr. Eldridge proposes a new grouping and 

 nomenclature for the middle Cretaceous in America. — There are 

 also papers on the gustatory organs of the American hare (Mr. 

 Tuckerman) ; on the output of the non-condensing engine, as a 

 function of speed and pressure (Mr. Nipher) ; and on some 

 Florida Miocene (Mr. Langdon). 



SOCIETIES AND ACADEMIES. 



London. 



Physical Society, November i. — Prof. Reinold, F.R.S., 

 President, in the chair. — The following communications were 

 read : — On a new electric-radiation meter, by Mr.W. G. Gregory. 

 The meter consists of a long fine platinum wire attached to a 

 delicate magnifying spring of the Aryton and Perry type, and 

 stretched within a compound tube of glass and brass. At the 

 junction between the wire and spring a small mirror is fixed. 

 When the tube is placed parallel to a Hertz's oscillator in action, 

 the mirror is turned in a direction indicating an extension of the 

 wire. The arrangement is so sensitive that an elongation of 

 •juoVou of a mm. can be detected, and when placed at a dis- 

 tance ,of 4 metres from the oscillator the apparent extension is 

 such as would correspond to a change of temperature of o°'oo3 C. 

 By its aid the author has roughly verified Hertz's statements 

 that at considerable distances the intensity of radiation varies as 

 the inverse distance ; but before he can proceed further it is 

 necessary to greatly increase the sensibility of the apparatus ; 

 and with a view of obtaining some suggestions in this direction, 

 he exhibited it before the Society. Prof Perry asked if the 

 E.M.F. required to produce the observed results had been cal- 

 culated ; he also believed that the sensibility might be increased 

 by using copper instead of platinum wire, and replacing the spring 

 by a twisted strip. Mr. Blakesley inquired whether the effect 

 of increasing the capacity of the ends of the wire had been tried. 

 Mr. Boys ^aid that if the observed effect was due to rise of 

 temperature he would like to see it measured thermally. He 

 also thought the effect might be due to extension caused by 

 rapid electric oscillations in some such way as the elongation of 

 an iron bar caused by magnetization. In answer to this, Prof. 

 S. P. Thompson said the matter had been investigated experi- 

 mentally, but with negative results. Prof. Herschel suggested 

 the use of a compound spring such as is used in Breguet's 

 metallic thermometers. In reply, Mr. Gregory said he had 

 estimated the E.M.F. by observing that a Leclanche cell 

 through 50 ohms produced about the same result. No improve- 

 ment in sensitiveness was obtained by using copper wire or by 

 increasing its capacity, and attempts to measure the rise of 

 temperature by an air thermometer had been given up as hope- 

 less. The President, in thanking the author lor his paper, con- 

 gratulated him on the ingenuity and courage displayed in pro- 

 ducing an apparatus to measure such microscopic quantities as 

 are here involved. — On a method of driving tuning-forks 

 electrically, by Mr. Gregory. In order to give the impulses 

 about the middle of the stroke, the fork is arranged to make 



and break the primary circuit of a small transformer, the 

 secondary circuit of which is completed through the electro- 

 magnet actuating the fork. The prongs of the fork are magnet - 

 ized and receive two impulses in each period. Another device- 

 was suggested, where the prongs respectively operate contacts 

 which successively charge and discharge a condenser througI< 

 the coils of the actuating magnet. Prof. S. P. Thompson saiti' 

 the methods, if perfect, would be of great service, and suggested 

 that a fork so driven be tested optically by comparison with a 

 freely vibrating one. He regarded the mercury contacts used 

 as objectionable, for their capillarity and adhesion would 

 probably cause the impulses to lag behind the appointed epochs. 

 Prof. McLeod remarked that Lissajous' figures gave a satis- 

 factory method of testing the constancy of period, and could be 

 readily observed without using lenses, and in reference to liquid 

 condensers suggested by the author for his second device, said 

 that platinum plates in sulphuric acid were found to disintegrate 

 when used for this purpose. He thought lead plates would 

 prove suitable. Prol'. Jones, who read a paper on a similar 

 subject in March last, said he now used bowed forks, with which 

 to synchronize the speed of the disk there described, and the 

 frequency is determined by causing the disk to complete tht- 

 circuit of his Morse receiver once each revolution. — On n 

 physical basis for the theory of errors, by Mr. C. V. Burton. 

 After pointing out that the law of error for any particular 

 measurement depends on the nature of the conditions governing: 

 such measurement, the author considers several simple cases, and 

 deduces their curves of error. A kinematic method of combin- 

 ing two or more independent errors, each following known laws, 

 is then described and applied, and the general formula obtained 

 leads to Laplace's law of error in the case of an infinite num- 

 ber of similar errors. Referring to Most Advantageous Com- 

 binations of measures, it is shown that the method of least 

 squares is only a particular solution of the general equation,, 

 and is derived by assuming the individual errors to conform to 

 Laplace's law. Subjective errors are next considered, and ir 

 conclusion the author says that "the law of error in a set of 

 observations depends on the nature of each special case, and 

 what may be called the probable law of error is determined by 

 our knowledge of the conditions. The combination of three or 

 more sources of error of comparable importance gives in general 

 a law not seriously differing from that of Laplace, so that the 

 method of least squares will be practically the most advantage- 

 ous, except where a single source of error with a very different 

 law is predominant above all the rest." — A note on the- 

 behaviour of twisted strips, by Prof. J. Perry, F. R.S., had 

 been prematurely announced by mistake, and he accordingly 

 gave only a brief outline of the paper. In a previous com- 

 munication, Prof. Ayrton and the author enunciated a working, 

 hypothesis in which the strips were imagined to be split up into 

 pairs of filaments, each pair acting as a bifilar suspension. The 

 resulting formula for the rotation produced by a given load did 

 not agree with experiment, and quite recently the author had 

 recognized why the formula was incorrect. The bifilar law they 

 had assumed was only true for small twists, but he now saw 

 another method of treatment by which he hoped to verify the 

 formula derived from experiment before the next meeting. Prof. 

 Fitzgerald reminded Prof. Perry of a method of attacking the 

 problem suggested by the speaker some time ago, in which each 

 filament was supposed to be wrapped round a smooth cylinder ;. 

 and said that on working it out the formula was found to be 

 very complicated. Mr. Trotter thought the pairs of strips 

 might be regarded as twisted ladders, and Mr. Gregory said this 

 suggestion reduced the problem to a series of bifilar suspensions- 

 which had already been worked out. — On electrifications due to- 

 contact of gases and liquids, by Mr. J. Enright. For som& 

 time past the author has been studying the electrical phenomena 

 attending solution, by connecting an insulated vessel in which 

 the solution takes place with an electrometer. As a general rule, 

 no effect is observed if nothing leaves the vessel, but when 

 gases are produced and allowed to escape the vessel become.s 

 charged with -}- or - electricity, depending on the nature of the 

 liquid from which the gas passes into the air. As an example, 

 when zinc is placed in hydrochloric acid, the deflection of the 

 electrometer is in one direction whilst the liquid is chiefly acid, 

 but decreases and reverses as more and more zinc chloride i-; 

 produced. From such observations the author hopes to obtain 

 some information relating to atomic charges. Owing to the 

 lateness of the hour, the latter portion of the paper and the 

 discussion on it were postponed until next meeting. 



