August 31, 1893] 



NATURE 



42: 



liquid, which was then lowered about halfway towards the 

 bottom. The liquid was stirred by a small turbine, and the 

 thermometer was so arranged that it only came into contact 

 with liquid which had ascended from the metal, and then had 

 been drawn down through the turbine tube, thus giving a very 

 rapid rise and gradual fall of temperature, as indicated by the 

 thermometer. The scale was read by a small microscope pro- 

 vided with two wires touching the scale, the meniscus being 

 brought midway between the two. This simple arrargemen 

 has the effect of eliminating all parallactic errors. 



The Comite International des Poids et Mesures has issued a 

 volume containing the proceedings of meetings held during 

 1892. M. L. Chappuis contributes to the volume a report of 

 an investigation of the thermal expansion of water by the « eight- 

 thermomeler method. lie has made two complete determina- 

 tions, one between o° and 42''4 C, and the other between 

 o°and 36'''6C. The results show that theexpansion of water from 

 0° to 40° is very closely given by the following e)(j>ression 

 -0-84 - 66-573253< - 8798939/- - 7-892005 x 10^-/3, 

 + S'i5S549 '^ lo"^/'*. M. C. E. Guillaume hrs prepared a 

 report on the metals employed in the construc'.ion of standard 

 scales, in which he recommends nickel as the best substance. 



COLO.NEL Waterhouse has been making experiments upon 

 the electrical action of light upon silver and its haloid com- 

 pounds, and communicated his results to the Anatic Society of 

 Bengal in May last. His arrangement was such that one plate 

 could be exposed to light while another with which it was in 

 electrical connection was screened from aclinic rays. From 

 the experiments it appears that, as a general rule, sunlight 

 has an oxidising or dissolving effect on silver, whether in 

 acid or alkaline solutions, the exposed plates being nearly 

 always positive, and consequently forming the anode of the 

 voltaic couple. With solutions decomposed by silver, and 

 forming sensitive compounds wilh it, the action is variable. 



Mr. p. Janet, in the current number of the Journal de 

 Physique, describes the methods he has adopted for experi- 

 ments on electric oscillations of comparatively long period, 

 tuocir second and thereabouts. Ilis object more particularly 

 is to obtain the actual form of the curves of intensity and 

 electro motive force, rather than to find the period and logar- 

 ithmic decrement. Wilh a modified form of interrupter of M. 

 Mouton's he is able to read accurately to suJ^u second, or even 

 less. A mica-condenser forms part of his arrangement, and he 

 was incidentally led to make experiments on the "hysteresis 

 and dielectric viscosity" of the mica, from the study of certain 

 variations which he found in the capacity of the condenser. 

 He sums up his results on this point thus: — " In a condenser 

 wilh solid dielectrics, under the influence of rapid [electric] 

 oscillations, there is a lagging of the charges behind the 

 differences of poteniial ; or, in other words, for equal differ- 

 ences of potenti.il, the charges are smaller with increasing 

 than wilh decreasing potentials." A new and apparently 

 accurate method for the determination of the coefficient of self- 

 induction is also given as a secondary result of the experiments. 

 In the same journal M. R. Malagoli gives a summary of his 

 theoretical investigations on electrolysis by alternating currents, 

 the results of which agree wiihthe experimental determinations 

 ofM. Mengarini. He concludes that the necessary and suffi- 

 cient condition under which electrolysis by alternating currents 

 is possible, is that the quantity of electricity passing through 

 the voltameter during a single alternation of the current must 

 be at least twice that which is necessary for the production of 

 the maximum polarisation of the voltameter. Electrolytic 

 production ceases when these two quantities become equal, 

 And the amount of the electrolyte decomposed is proportional 

 o their difference. 



NO. 1244, VOL. 48] 



At the meeting of the Paris Academy of Sciences on 

 August 14, MM. Delahaye and Boutille showed an ingenious fire- 

 alarm. A hollow ball of aluminium, 15 to 20 mm. in diameter, 

 is supported at one end of an arm, with a counterpoise at the 

 other end, the whole being in equilibrium at the ordinary 

 temperature and pressure of the air. The apparatus is jnir- 

 posely made not sensitive enough to show the ordinary natural 

 changes of pressure, but if the specific gravity of the air be- 

 comes diminished considerably, either from a rise of tempera- 

 ture or an admixture of coal gas in sufficient quantity to become 

 explosive, the balance is destroyed, and the ball in falling 

 completes an electric circuit by which an alarm bell is set 

 ringing until the normal state of affairs is again established. 



Sir Charles Todd has issued a report on the rainfall in 

 South Australia and the northern territory during 1892, with 

 the weather characteristics of each month. 



GusTAV Fischer, of Jena, has recently published second and 

 revised editions of two well-known books — Prof. E. Stras- 

 burger's " Kleine Botanische Practicum," and Prof. Richard 

 Hertwig's " Lehrbuch der Zoologie." 



Messrs. Crosby Lockwood and Son will publish in 

 September a comprehensive handbook on " Practical Building 

 Construction," by Mr. J. P. Allen, lecturer at the Durham 

 College of Science, Newcastleon-Tyne. The work will be 

 illustrated by about 1,000 diagrams. 



With reference to the article on the " Position of Scientific 

 Experts" in our issue of the 17th inst. a correspondent informs 

 us that for some years it has been legal for a judge to select an 

 expert to report to the Court upon a particular matter in dis- 

 pute, and this practice is occasionally followed. The mode of 

 selection and of appointment, and the status of the official 

 English expert, are therefore almost identical with those of his 

 German equivalent. 



The Isle of Man Natural History and Antiquarian Society 

 visited the Marine Biological Station at Port Erin on August 14, 

 iind Prof. Herdman, F. R .S., the director of the station, gave 

 the members an address upon the objects and methods of 

 marine biology. We understand that it is intended to con- 

 struct fish hatcheries at Port Erin, and to wall in several of the 

 creeks round the coast for the preservation of young fish until 

 they reach maturity. 



An "Electrical Engineer's Price-Book," edited by Mr. H. 

 J. Dowsing, has been published by Messrs. Charles Griffin and 

 Co. It contains a large amount of information on the com- 

 mercial aspect of electrical work, and should be of great 

 assistance, not only to electrical engineers, but also to borough 

 engineers, architects, railway contractors, and local authorities 

 who desire to be informed upon matters connected with elec- 

 trical installations. 



Brazil produces, on the average, about 360,000 tons of coffee 

 per annum, that is, about four-fifths of the whole amount con- 

 sumed in the world. Since the Slate of Sao Paulo alone pro- 

 duces one-half of this quantity, an illustrated ptimphlet by St iior 

 AdolphoA. Pinto, one of the Commissioners of the State at the 

 World's Columbian Exposition, would be expected to contain 

 an accurate account of coffee cultivation. The little pamphlet 

 justifies the expectation. Every one interested in coffee-growing 

 in general, and in Sao Paulo in particular, will find it well 

 worth reading. 



It was generally admitted by those competent to judge that 

 the display of scientific instruments at the Paris Exposition of 

 1889 was inferior to that of 1878. There were, however, a few 

 striking exhibits scattered in different classes in an unaccount- 

 able manner. Mr. A. Lawrence Rolch was appointed to report 



