November 11, 1904.] 



SCIENCE. 



651 



ume, he will be interested in ' Principles of 

 Animal Nutrition,' by H. P. Armsby, director 

 of the Pennsylvania State Agricultural Ex- 

 periment Station, which discusses this and 

 related topics and summarizes a large amount 

 of interesting information. The question is 

 also taken up by Dr. Armsby in ' The Iso- 

 dynamic Eeplacement of Nutrients,' Science, 

 N. S., 18 (1903), No. 459, pp. 481-487. 



Some experiments which have to do with 

 temperature during fever with especial rela- 

 tion to the influence of the abnormal body 

 condition on metabolism are summarized in 

 Bulletin No. 45 of the Office of Experiment 

 Stations, entitled ' A Digest of Metabolism 

 Experiments.' 



The Jahreshericht der Tier-Chemie con- 

 tains numerous titles and abstracts of articles 

 which deal with the question under consider- 

 ation. The Department of Agriculture li- 

 brary contains a set of this journal, which 

 can undoubtedly be found also in a number 

 of other public or university libraries. 



0. F. Langwoethy. 



Office of Expekiment Stations, 

 Department of Agriculture. 



mathematics and metaphysics. 



On reading the interesting lecture of Pro- 

 fessor Josiah Eoyce on ' The Sciences of the 

 Ideal,' and learning that all leveling and serial 

 relations come from the same root, one is re- 

 minded of the computer of the coast survey, 

 who decided that 8 X 8 is not exactly 64, but 

 plus or minus a small quantity, according to 

 the table of logarithms he used. If mathe- 

 matics and metaphysics coalesce where shall 

 we rest? Will our .mathematicians become 

 'flabbier and flabbier'? A. Hall. 



October 10, 1904. 



SPECIAL ARTICLES. 



what is an ELECTRIC CURRENT?* 



The question of the day which seems to ap- 

 peal most strongly to the physicist is : What 

 is taking place in a metallic conductor on the 

 terminals of some electrical source? 



* Abstract from an address on ' Present Prob- 

 lems in Physics,' at the Congress of Arts and 

 Science. 



Rowland's rotating disk showed that a posi- 

 tively charged body moving in a positive direc- 

 tion, and a negatively charged body moving 

 in an opposite direction, produce the same 

 electromagnetic effects in the surrounding 

 field. 



Rutherford's work in deflecting the electrons 

 of a radioactive body is in entire harmony 

 with Rowland's result. Positively charged 

 masses of radiant matter are deflected in the 

 opposite direction from negatively charged 

 matter, when acted upon by a magnetic field, 

 the masses are, of course, moving in the same 

 direction. These charged particles of mov- 

 ing matter are, in effect, superposed, or per- 

 haps juxtaposed electric currents moving in 

 the same direction. If either the a or the p 

 particles could be reversed in direction, then 

 the magnetic field would deflect them in the 

 same direction. They would then each create 

 the same external magnetic effects. They 

 would then represent superposed currents of 

 opposite sign, moving or flowing in opposite 

 directions. 



All of this means that a positive current of 

 electricity flowing in a positive direction is 

 not a negative current of electricity flowing in 

 a negative direction. These two currents in- 

 volve the motion of masses of matter in op- 

 posite directions. Do these currents co-exist 

 in the conducting wire? Is a direct-current 

 dynamo pouring oppositely moving electrons 

 into the opposite ends of the conductor? 

 After a few thousand years of continuous use, 

 may it become clogged and lose in part its 

 conductive properties, acquiring perhaps 

 meanwhile radioactive properties? 



Wheatstone made a famous experiment on 

 the discharge of a Leyden jar, which was 

 thought very instructive in his day. But 

 did his contemporaries really learn the lesson 

 which that experiment teaches. The sparks 

 at the two gaps nearest the terminals of the 

 conductor were formed before the central 

 spark appeared. Have we not here evidence 

 that the positive and negative currents, mov- 

 ing in opposite directions, begin at the opposite 

 terminals, and only become superposed after 

 an appreciable time interval? 



In a Geissler tube having a length of about 



