70 



NA TURE 



[November i8, 1897 



that this alteration would make a much greater difference in the 

 number of pupil-teachers working for sessional certificates than 

 has been the case. They have been much gratified by the en- 

 thusiasm shown by the heads of pupil-teachers' centres with 

 regard to University Extension teaching, in their efforts to keep 

 in connection with the Society under the altered conditions. 

 Pioneer courses of lectures, the expenses of which have been 

 borne by the Technical Education Board of the London County 

 Council, have been given at Bethnal Green, Poplar, Queen's 

 Park, St. Pancras, Shoreditch (two courses), Walworth (two 

 courses), and Wandsworth. These courses were attended by 

 about 3500 people, almost exclusively of the artisan class. The 

 average attendance at each lecture was 387. In two of the dis- 

 tricts regular extension centres have been formed as the result of 

 the lectures. In connection with these courses the illus- 

 trations of scientific principles are largely drawn from the in- 

 dustrial developments of the district with which the working 

 men are particularly acquainted. Thus the course on " Electric 

 Power and Lighting," given by Dr. Laurie at the Town Hall, 

 Shoreditch, in the Lent Term, was fully illustrated by views of 

 the Shoreditch electric installation, and created an intense 

 interest in the subject among the working men, who attended in 

 great numbers. A large proportion of the audience remained 

 for class instruction after the lectures ; many did regular weekly 

 paper work, and forty obtained the certificates of the Society as 

 the result of the terminal examination. 



SCIENTIFIC SERIALS. 



American Journal of Science, November. — Geology of 

 Southern Patagonia, by J. B. Hatcher. This is an account of 

 the results of an expedition mto Argentine Patagonia made for 

 the purpose of collecting vertebrate fossils for Princeton Univer- 

 sity. The oldest sedimentary deposits seen were a series of 

 black, very hard, but much fractured slates, with Ammonites 

 fairly abundant, but not sufficiently well-preserved to admit of 

 identification. These beds are referred to the Jurassic, chiefly 

 on account of their lithological characters and the great thickness 

 of the overlying rocks, which, to judge from Dinosaurian remains, 

 can hardly be more recent than the Cretaceous. The beds of 

 basalt observed by Darwin on ascending the Santa Cruz River 

 are not due to a flow from the distant Cordilleras, but to small 

 local craters. — The former extension of the Appalachians across 

 Mississippi, Louisiana, and Texas, by J. C. Branner. Gives 

 additional facts in support of his thesis that the old Appalachian 

 land area crossed what is now the lower Mississippi valley. The 

 coal-measures drainage of the Illinois-Indiana-Kentucky basin 

 flowed westward through the Arkansas valley into a carbon- 

 iferous Mediterranean sea. The drainage of the coal-measures 

 region south of the Ouachita anticline flowed westward and 

 entered this sea north of the Texas pre-Cambrian area. The 

 drainage of both the Arkansas and Texas carboniferous areas 

 was reversed about the end of Jurassic times, when orographic 

 movements over south-east Arkansas, eastern Texas, Louisiana, 

 and Mississippi submerged the former extension ol the Appa- 

 lachian watershed, and admitted the early Cretaceous sea across 

 the Palaeozoic land as far north as southern Illinois. — The com- 

 bustion of organic substances in the wet way, by I. K. Phelps. 

 Carbon dioxide may be estimated iodometrically with a fair 

 degree of accuracy. It may, therefore, be applied to the de- 

 termination of organic carbon oxidised by liquid reagents, such 

 as potassium permanganate or chromic acid. The former was 

 used for oxidising oxalates, formates, and tartar emetic ; the 

 latter for these and cane-sugar and paper. The method is very 

 successful in the case of the less volatile organic compounds. — 

 Some features of the pre-glacial drainage in Michigan. In all 

 the glaciated area of North America no region is so extensively 

 and deeply covered with drift as the lower peninsula of Michigan. 

 The author works out the probable features by analogy with 

 unglaciated areas, and constructs a map showing the probable 

 carboniferous river system. 



Wiedemann'' s Annalen der Physik und Chemie, No. 10. — 

 Observation of Zeemann's phenomenon, by W. Konig. The 

 author observes the dark sodium lines produced by an arc light 

 traversing a sodium flame. The broadening in a magnetic field 

 is detected by a differential method. A quarter-wave plate and 

 a doubly- refracting prism are used to obtain two images of the 

 slit joining across a narrow line. The extinction of the circu- 

 larly-polarised right-hand edge in one image, and the left-hand 



edge in the other, gives the appearance of a lateral displacement 

 which is reversed by turning the prism. A total displacement 

 of i/28th of the distance between the D lines is thus obtained 

 in a field of 7300 units. — On the rate of depolarisalion of elec- 

 trodes and on dielectric constants at low temperatures, by R. 

 Abegg. This is a criticism of Dewar and Fleming's alleged 

 enormous capacities of certain dielectrics at very low tempera- 

 tures. The author maintains that these are only apparent, and 

 are really due to the very slow depolarisation of electrodes in 

 great cold, so that the current obtained from the condenser is a 

 polarisation current instead of being a dielectric current. — On 

 the depolarisation of mercury and platinum electrodes, by K. R. 

 Klein. Large and small electrodes dipped into various acid 

 and salt solutions, and the course of their polarisation by a 

 known E.M.F. and their subsequent depolarisation, was 

 investigated by means of a capillary electrometer of negligil)le 

 capacity. It was found that the rate of depolarisation was ncarl) 

 independent of the area of the electrode and of the nature of the 

 solution, but was much accelerated by heat and by the presence 

 of a salt composed of the electrode metal as a base, and the acid 

 of the electrolyte. — An electro-chemical method of converting 

 alternating into direct currents, by L. Graetz. Cells in which 

 aluminium forms the anode do not transmit currents having a 

 voltage below 22. Alternating currents may therefore be con- 

 verted into intermittent currents by means of a battery of such 

 aluminium cells. The author describes an arrangement for 

 obtaining a direct pulsating current by the same means The 

 apparatus forms a convenient " rectifier." — Researches on lamp- 

 black, by J. Stark. The specific gravity of solid lampblack is 

 forty-three times that of lampblack as deposited. One cc. con- 

 tains 1,270,000 million particles of lamp black. The author 

 obtained polished surfaces of lampblack, and proved that as 

 regards elliptic polarisation they occupy a place intermediate 

 between transparent substances and metals. 



SOCIETIES AND ACADEMIES. 

 London. 



Physical Society, November 12. — Mr. G. Johnstone 

 Stoney, Vice-President, in the chair. — Mr. J. Rose-Innes read 

 a paper on the isothermals of ether. The well-known general- 

 isations of Boyle and Gay-Lussac with regard to the pressure, 

 volume, and temperature relations of gases, vyere examined by 

 Ramsay and Young, who deduced the law p — bt — a, i e. 

 that pressure is a linear function of temperature, at constant 

 volume, where b and a are functions of volume only. It yet re- 

 mains to discover the form of these two functions b and a. The 

 author finds b and a for a large number of volumes, and from 

 them devises an empirical formula. As a preliminary step he 

 examines whether any single algel)raical expression can repre- 

 sent the case, so as to determine the probability of discontinuity. 

 For this purpose a graphic method is applied. By plotting 

 (az/^)~\ against f's, a curve is obtained of " cusp " shape. The 

 point of the cusp occurs very near critical' volume, it suggests 

 discontinuity in the slope of {av^)"^. The author concludes that 

 there is extremely rapid change of behaviour of the gas at this 

 point. Again, it is known that the temperature at which pres- 

 sure is accurately given by the laws of a perfect gas at a par- 

 ticular volume, is constant for large volumes until critical volume 

 is approached. The author observes that at the critical volume 

 this temperature diminishes somewhat from its value for large 

 volumes. These conclusions were embodied in a previous 

 paper, and an algebraical expression for pressure in terms of 

 temperature and volume were then given for isopentane. In 

 the present paper the author investigates a similar formula for 

 ether. Prof. Ramsay said that experimental errors might 

 account for some of the lack of agreement between proposed 

 formulae and direct observation of the behaviour of gases. 

 Isopentane was probably a better-investigated body than ether, 

 for it was simpler. Ether tended to form complex molecular group- 

 ings, but isopentane was probably a mono-molecular liquid. Prof. 

 Perry did not quite agree with the author's conclusions. It was 

 necessary to distinguish between a formula founded on a physical 

 hypothesis, and a mere empirical formula. The author had 

 assumed that the Ramsay and Young formula was very exact, its 

 originators did not put it forward as being infinitely exact. 

 Probably the best test for such a formula as that under discussion 

 would be derived from some thermo-dynamical conclusion 

 deduced from it. The Rose-Innes formula, with five constants 



NO. 1464. Vt^L. 57] 



