638 



NATURE 



[October 27, 1904 



A'allentin's article is illustrated by a photograph of a 

 " rookery " of rock-hopper penguins (Eudyptes chrysocome), 

 showing the myriads in which these birds congregate on 

 the coasts, and by a second (herewith reproduced) of a 

 much smaller assemblage of gentu penguins {Pygoscelcs 

 tacniata). An interesting fact in connection with the habits 

 of the rock-hoppers is that the smooth surfaces of the hard 

 igneous rock over which these penguins have passed for 

 generations are not only highly polished, but are marked 

 by irregular groovings made by their claws. These 

 scratches are usually about 3 inches in length, and may 

 be as much as a quarter of an inch in depth. Apparently 

 such a polished and striated rock-surface might well be 

 attributed to ice-action. A striking feature about such a 

 rookery is the number of dying and maimed birds to be met 

 with ; such injuries appear to have been inflicted by seals 

 or sea-lions. The enormous number in which the " molly- 

 mauks " frequent the Falkland and other Antarctic islands 

 may be inferred from the statement that on one occasion a 

 vessel arrived at the main port with a cargo of 10,000 eggs 

 of this species. Mr. Vallentin found these beautiful birds 

 so tame and confiding that they allowed themselves to be 

 stroked by his hand as he admired the softness of their 

 plumage and its spotless condition. How these birds keep 

 themselves clean amid the liquid filth of a rookery is little 

 short of a marvel. R- L- 



THE Sr. LOUIS INTERNATIONAL 

 ELECTRICAL CONGRESS. 

 T^HIS congress, during its five working days, considered 

 about 160 papers on electrical subjects. In fact, so 

 large was the number of papers and so wide the range of 

 subjects of which they treated, that it may be said that 

 there is no branch of electrical science which 'was not re- 

 ferred to at one time or another during the meetings. 

 Nevertheless, the chief scientific interest in the proceedings 

 centred round a few subjects, namely, units and standards, 

 radio-activity, wireless telegraphy, and the electric arc. Of 

 the engineering papers, those on the alternating current 

 motor, the steam turbine, and high tension transmission 

 attracted most attention. There were also numerous papers 

 on electrochemical and electrotherapeutical subjects, which 

 will not be referred to here. 



The joint discussion by Section A, general theory, and 

 Section B, general applications, on units and standards was 

 opened with papers by Prof. Ascoli (systems of electric units). 

 Profs. Carhart and Patterson (absolute value of the E.M.F. 

 of Clark and Weston cells), and Dr. Wolff (international 

 electric units). The subject divided itself into two parts : — 

 (i) the true value of the volt and ampere; (2) which of 

 these should be represented by a material standard, and the 

 nature of that standard. During the discussions the naming 

 of the magnetic units was also considered. 



Upon the question of the true value of the volt and ampere 

 there was practical unanimity of opinion that the true value 

 of the volt (10' C.G.S. units) is such that the E.M.F. of a 

 standard Clark cell at 15° C. is very much nearer 1-433 volts 

 than 1-434, '^'^ present legal value. Profs. Carhart and 

 Patterson, in describing the dynamometer with which they 

 are making a re-determination of the ampere, stated that 

 though the experiments were not sufficiently advanced to 

 give a definite value, the results so far obtained made the 

 E.M.F. of the Clark cell about 1.433 volts, accepting the 

 ohm as correct. In this connection Mr. Trotter's results, 

 mentioned by Dr. Glazebrook, are of great interest. Mr. 

 Trotter has recently made a determination of the E.M.F. 

 of the Clark cell at the Board of Trade laboratory in terms 

 of the standard ampere and standard ohm, and finds the 

 value to be 1-4320 volts at 15° C It would thus appear 

 that the voltage of a normal Clark cell, determined in terms 

 of our standard ampere and ohm, is nearly i/io of i per 

 cent, less than the legalised value. The Reichsanstalt take 

 the value of the Clark cell at 14328 volts. It is of interest 

 to note that the present legal value of 1-434 appears to be 

 almost exactly correct at 14° C. instead of 15° C. 



.Mr. Barnes, in his paper on the mechanical equivalent of 

 heat measured by electrical means, -n'hich contains a very 

 careful comparison of the results obtained both by the 

 electrical and mechanical methods, takes the Clark cell as 



1.43325 volts, and then finds that the " results by the con- 

 tinuous electrical method is brought into absolute agreement 

 with the «!c<i'i of the mechanical measurements," and he 

 gives the value of the mechanical equivalent as 4-186 joules- 

 in terms of the mean calorie betw-een 0° and 100°. 



The standards which are to represent the fundamental 

 electrical units raised quite another set of questions, the 

 main desiderata for these standards being that they should 

 be both permanent and reproducible to a high degree of 

 accuracy. No one appeared anxious to quarrel in any way 

 with the standard mercury ohm, and the agreement of the 

 standards lately made by the National Physical Laboratory, 

 both with one another and with those constructed by the 

 Reichsanstalt, shows that this standard is reproducible to a 

 few parts in 100,000. Accepting the present ohm standard, 

 it is only necessary to legalise a standard for either the- 

 ampere or the ohm, as the three units are connected by 

 Ohm's law. Prof. Carhart and Dr. Wolff urged the de- 

 sirability of defining the volt in terms of a cell, preferably 

 the cadmium cell, and the ampere in terms of the volt and 

 ohm, the advantages being that the standard cell is very 

 generally used in practical measurements both of potential 

 difference and current, and that the cells are reproducible 

 to a high degree of accuracy. Dr. Glazebrook pointed out 

 that the greater simplicity of the chemical changes in the 

 deposition of silver gave promise of its being an even more 

 accurate standard for the ampere. 



Prof. Carhart and Mr. Hulett, in their paper on a study 

 of the materials used in standard cells and their prepar- 

 ation, trace the difficulties with cells both of the Clark 

 and Weston (cadmium) type to the mercurous sulphate : 

 they describe an electrolytic method of preparing it, and' 

 they strongly emphasise the importance of avoiding 

 hydrolysis of the mercurous sulphate. In a table in the 

 paper they give the results obtained with fourteen cadmium 

 cells made according to their method, from which it appears, 

 that the maximum difference between the voltages of in- 

 dividual cells and between the voltages of the cells during 

 the whole seven months that the tests lasted did not exceed 

 5 parts in 100,000, so that, taking any cell at any time 

 during the tests, its voltage could be depended on to within 

 + 0-03 millivolt of the mean voltage. Similar excellent 

 results have been obtained by Mr. Smith at the National 

 Physical Laboratory (report to British .Association, Cam- 

 bridge). 



In view of the large amount of work which is now being 

 carried out on the preparation of standard cells and the re- 

 determination of the ampere, the general feeling of the 

 meeting seemed to be that international action to correct 

 the error in the volt should be postponed, although one 

 speaker urged that the error of o. i per cent, in the volt had 

 become of serious commercial importance in the life tests of 

 incandescent lamps. 



Prof. Wolff's paper, which dealt largely w'ith the legal 

 definitions of the fundamental units adopted by various; 

 nations, pointed out the great differences which exist, and 

 the necessity of rendering them all uniform. 



On the subject of naming the magnetic units there was 

 very little discussion ; the question of 4ir, of course, came 

 up, and was discreetly left on one side, most of the meet- 

 ing "agreeing with Dr. Kennelly that it is better to let well 

 alone, and that no very great practical advantage would 

 result from the change. The views of the I.E.E. delegates, 

 that if any magnetic units -were named they should be those 

 proposed by Dr. Kennelly, viz. the C.G.S. units of mag- 

 netic potential (already called the Maxwell at the Paris 

 congress), total magnetic flux, and magnetic reluctance, 

 met with pretty general acceptance. The other proposal 

 made by Dr. Kennelly, namely, to add the prefi.x " ab " 

 or *' abs " to the names of the practical units to form names 

 for the corresponding C.G.S. units in the electromagnetic 

 and electrostatic systems, so that " abvolt " would be the 

 name for the C.G.S. unit of difference of potential in the 

 electromagnetic system, and absampere for the C.G.S. 

 unit of current in the electrostatic system, led to no dis- 

 cussion, the I.E.E. delegates simply expressing their dis- 

 approval of this proposal, which made the same prefix have 

 different numerical values according to the name it pre- 

 ceded. 



The chamber of Government delegates, to w'hich Cire.'it 

 Britain .-ippointed at the last moment Colonel Cromplon, 



NO. 1826, VOL. 70] 



