JtTLT 24, 1914] 



SCIENCE 



121 



in the same colmnii and have the same 

 atomic number, but that their atomic 

 weights differ by 4. Such substances have 

 chemical properties so identical that they 

 are called inseparables, or non-separables, 

 or isotopes, for they occupy the same place 

 in the periodic table. Thus the old trouble 

 of finding places in the periodic table for 

 the thirty or forty radiant elements has 

 suddenly vanished. They may be super- 

 posed even when their atomic weights differ, 

 if their atomic numbers are the same. The 

 nuclear charges of isotopes must be iden- 

 tical, but the distribution of electrons may 

 be different. Other examples of insepa- 

 rables are: 



Lead, radium B, Radium D, all 82. 

 Thorium and radiothorium. 

 Eadium and mesothorium. 

 If these views are distasteful to chemists 

 let them discover some means of the sepa- 

 ration of the known isotopes. 



It must be further noted that the results 

 of radiochemistry appear to require the 

 presence of negative electrons in the nu- 

 cleus itself. The expulsion of a ;8 particle, 

 or one negative electron, from the nucleus 

 is equivalent to the gain of one positive 

 electron, and involves a unit increase in 

 the atomic number. 



14. The last advance is the most impor- 

 tant and far-reaching. There has been long 

 search for the positive electron, and in vain ; 

 yet it seems likely that it has been under 

 our eyes all the time. Since the hydrogen 

 atom never loses more than a single elec- 

 tron, is it not possible, suggests Rutherford, 

 that the nucleus of the hydrogen atom may 

 be the positive electron? 



The electro-magnetic mass of an electron 



.2a 



IS - -; where e is the charge and a the 

 6 e'' ° 



radius. If the mass of the hydrogen nu- 

 cleus is wholly electro-magnetic, then its 

 radius must be smaller than that of the 



electron (negative) as 1 : 1800, for that is 

 the ratio of their masses, while their 

 charges are equal and opposite. Hence we 

 have 



Mass Diameter 



Atom 1 10-8 cm. 



Negative electron 1/1800 10-is 



Positive eleotron 1 10-i« 



Rutherford cautiously remarks that there 

 is no experimental evidence against such a 

 supposition. 



Those who wish to follow the matter 

 deeper must refer to many articles in the 

 Philosophical Magazine,^ several letters to 

 Nature, Soddy's "Chemistry of the Radio- 

 elements," part II., and Perrin's "Les 

 Atomes." The chief writers have been 

 Rutherford, W. H. Bragg, "W. L. Bragg, 

 G. C. Darwin, Moseley, Broek, Bohr, 

 Russell, Fajans, Soddy, Hevesy, Nicholson 

 and Mardsen. 



Much has yet to be done, and much to bo 

 revised, but that the first great forward 

 strides have been taken in the right direc- 

 tion there can be little doubt. 



A. S. Eve 



McGiLL Univeesitt, 

 May. 1914 



STATISTICS OF CHOPS 



DEGREE OP ACCUEACT OF THE REPORTS OF THE 



BUREAU OF STATISTICS OF THE UNITED STATES 



DEPARTMENT OF AGRICULTURE 



In the March 28, 1913, number of Sciencb, 

 Dr. C. G. Hopkins gives a discussion of this 

 topic under the title of " Facts and Fiction 

 about Crops." The Department of Agricul- 

 ture is accused of " condemnable inflation of 

 crop statistics." The writer does not believe 

 that such a conclusion would be reached if the 

 reports were more carefully studied. 



He shows the percentage of error to be very 

 great when the Bureau of Statistics estimates 

 of corn in the southern states are compared 

 with the census report. If the error is due to 

 wilful deception, we should expect to find the 



