500 



NA TURE 



[June 



1910 



per c.c. being also large, ranging up to a million or more. 

 The electrical quantities to be measured were thus of con- 

 siderable magnitude. 



Part viii. of the Verhandhmgcn der deutschcn physik- 

 alischen Gescllschaft contains a paper by Dr. H. G. Moller 

 on the calculation of the Foucault currents in iron. He 

 considers the case of a cylinder of iron surrounded by a 

 coil through which an alternating current is sent, and 

 calculates the magnetic induction at any instant, taking 

 into account the induced currents produced in the iron 

 itself. With 100 cycles per second the B-H curves for low- 

 values of the maximum impressed H are almost identical 

 with the ordinary magnetisation curves, but as the value 

 of H is increased the hysteresis loop contracts near the 

 origin. This result is in exact accord with the experi- 

 ments made last year by Dr. Plausrath, and justifies the 

 conclusion that the magnetisation in iron responds 

 instantaneously to changes in the resultant, magnetising 

 force. 



We have received from Prof. Merczyng, of St. Peters- 

 burg, a separate copy of his paper on the indices of refrac- 

 tion of liquids for electric waves of small wave-length, 

 which appeared in the April Bulletin of the Academy of 

 Science of Cracow. The electric waves were generated by 

 a Righi oscillator, and were measured by means of the 

 interference produced by reflection at two metal surfaces, 

 one a little in front of the other. The measurement gave 

 4-5 cm. The indices of refraction of the liquids were 

 calculated by Fresnel's formula from observations of the 

 relative intensities of the incident beam and the beam 

 reflected from the surface of the liquid. They lie, for the 

 five liquids tested, between the indices found previously 

 by the late Prof. Drude for waves of 75 cm. and the 

 values for light waves. 



A SERIES of measurements of the temperatures of the 

 metallic filaments of incandescent electric lamps has 

 recently been made by Dr. M. v. Pirani at the lamp works 

 of Messrs. Siemens and Halske, and the results are given 

 in part vii. of the Verhandlungen der deutschcn physik- 

 alischen Gesellschaft. The filaments were of platinum, 

 tantalum, and tungsten, and were, in general, stranded. 

 They were heated in an inert gas or in vaciio either by 

 an external heating coil or by the current traversing them, 

 and the temperature was measured by a standardised 

 thermo-element of fine wire introduced between the 

 strands. Up to a temperature of 1600° C.' it was found 

 that temperature t and current i were connected by the 

 relation i = a+b.i", where a and b are constants and n 

 has a value between 1-5 and 25. This relation was used 

 to determine the temperature above 1600° C. Observa- 

 tions were also made of the " black-body temperature " 

 of the filaments by a standardised radiation thermometer 

 of the Holborn-Kurlbaum type using red light. Tables 

 are given of the resistances of the filaments up to tempera- 

 tures just below the melting points, and it is shown that 

 at these points the black-body temperatures are about 

 150° C. below the actual temperatures. 



The quality of surface waters in the United States, by 

 Mr. R. B. Dole, is the subject of water-supply paper 

 No. 236, issued by the United States Geological Survey. 

 The numerous analyses are chiefly of local interest, but 

 the account of the methods employed is worthy of note. 

 The highest accuracy consistent with rapidity of analysis 

 was aimed at, and an estimate is given of the limits of 

 accuracy achieved for each constituent. The methods of 

 presenting the results of water analyses are also discussed, 

 the ionic form of statement being regarded as the best, as 

 it gives a statement of facts and not of opinion. 



NO. 2 12 I, VOL. 83] 



The Stumpf uni-directional flow steam (engine forms tJK 

 subject of an illustrated article by Prof. Stumpf, of th« 

 Charlottenburg Technical High School, in Engineering foi 

 June 10. In this engine the steam is carried through th« 

 engine in an unchanged direction. The live steam ii 

 admitted from below into the cover, which it serves t< 

 jacket, and enters the cylinder through the valve. At the 

 completion of the working stroke it is exhausted through 

 slots or ports which are provided in the middle of the 

 cylinder, and are uncovered by the piston. This avoids th( 

 losses common to ordinary engines by the cooling of the live 

 steam ports produced by the flow of wet exhaust stean: 

 through them, and the consequent condensation in the 

 cylinder. Prof. Stumpf claims that the remarkable 

 advantages off'ered by this type of exhaust, notably the 

 great simplicity of construction, render the uni-directiona 

 flow principle particularly valuable for engines working 

 with superheated steam. Stationary and portable Stump: 

 engines of a great variety have already been built on the 

 Continent, and their manufacture has been taken up ir 

 this country. 



Co.\iMENTiNG on the salving of the French submersible 

 boat Pluviose, Engineering for June 17 states that the 

 practice in all British submarines is to have a diving 

 dress for each member of the crew stowed away adjacen 

 to the station which he occupies when the boat is sub 

 merged. There is a flexible lead from the usual aii 

 service, with a valve in close proximity to each dress. It 

 the event of an accident the dress can be put on in hal 

 a minute and supplied with air by means of the flexible; 

 lead. A purifier is fitted to the dress, which ensures i 

 supply of air sufficient to last the man for an hour and s 

 half. Training of the members of the crew to effect exit 

 in the British service, is conducted in a tank, the botton 

 of which is fitted up to resemble a submarine boat, ane 

 the test imposed upon the prospective members of a crev 

 is to plunge to the bottom of the tank in an air lock, when 

 he is required to put on the diving dress, proceed acros! 

 the tank, ascend the counterfeit of a conning-tower in ; 

 submarine, and open the hatch, when he is enabled t< 

 rise to the surface. The period occupied for training th' 

 men in this important work has been found by experieno 

 to be not more than five days. Although the condition 

 are not quite those existing in a submarine after ai 

 accident, yet the method appears to offer the only likel] 

 solution of a very difficult problem ; it is simple, ane 

 provides, at any rate, that each member of the crew wil 

 have a chance of saving his life. 



W'e have received from the Caxton Publishing Company 

 Ltd., the first volume of " Nature-study on the Black 

 board," by Mr. W. P. Pycraft and Miss J. H. Kelman, t« 

 be completed in three volumes at ys. 6d. net each. W' 

 hope to review the work when the remaining volumes ar 

 available. 



A SEVENTH edition of Mr. Charles Pendlebury' 

 " Exercises and Examination Papers in Arithmetic 

 Logarithms, and Mensuration " has been published b; 

 Messrs. G. Bell and Sons, Ltd. About two-thirds of th 

 contents of the present issue consist of new matter, ani 

 the portions of the older book which have been retain© 

 appear in a somewhat different order. 



The Selborne Society has issued the third of a serie 

 of leaflets on the Brent Valley Bird Sanctuary. This deal 

 with curious nesting places, and, like those previous! 

 issued, is profusely illustrated, having been reprinted fron 

 The Country Home. Copies of the leaflet may be obtain© 



