NOVBWBEE 7, 1902.] 



SCIENCE. 



745 



of formation is directly proportional to the 

 number of atomic unions in the molecule. 



3. The absolute heat of formation of any- 

 organic compound is a multiple, by a whole 

 number, of a single constant. The latter is 

 identical with the neutralization constant, and 

 has a value somewhere between 13,700 and 13,- 

 800 calories. 



4. The thermal value of a union between 

 two atoms is independent of their masses. 



5. The absolute heats of formation of cor- 

 respondiiag chlorides, bromides and iodides are 

 equal. 



The last conclusion at once suggests a cor- 

 relation between thermochemical data and 

 Faraday's law. Trom this point of view, the 

 latter may become part of a wider generaliza- 

 tion whose details are yet to be worked out. 



Mr. J. D. Thompson then explained the 

 principles of the ' Keclassification of the Sci- 

 ence Section at the Library of Congress.' All 

 the books in the library are to be grouised in 

 twenty-six classes, lettered A to Z; Q is as- 

 signed to science; a second letter gives the 

 first subdivision, and then follow numbers, as 

 Q A 503; in a second line the familiar Cutter 

 author-abbreviations are given. The division 

 is to be rather minute since access to the 

 shelves will be liberally granted to students. 

 It is expected that ultimately the library will 

 have a card catalogue of all the other Wash- 

 ington libraries. 



C. K. Wead, 

 Secretary. 



DISCUSSION AND CORRESPONDENCE. 



GUESSES ON THE RELATIVE WEIGHTS OF BILLS AND 

 ' COINS. 



In Science for April 25 an account was given 

 by Mr. J. Pranklin Messenger of certain re- 

 sults obtained in reply to the question, ' How 

 many one-dollar bills will equal in weight a 

 five-dollar gold piece ? ' The answers revealed 

 a quite startling notion either of the heaviness 

 of the coin or of the lightness of the bill, the 

 average guess being 2,291 for 97 students of 

 Coliunbia University and 2,749 for a class of 

 students in the University of Kansas. The 

 correct answer should have been about 7. The 



writer of the article used only those results 

 that were obtained from male students, some- 

 what disparagingly remarking that he had 

 omitted the replies of the women because of 

 their great variation. Since the feminine 

 power to make reliable, or at least utilizable, 

 estimates of this nature was thus called in 

 question, I determined to put the same query 

 to a class of 175 students in Smith College. 

 The results were by comparison so gratifying 

 that it may be of interest to state them. 



A few had heard of the question before and 

 were more or less sure of the correct answer. 

 Their replies were, of course, excluded, leaving 

 162 replies for consideration. The average 

 estimate was 108, as compared with the above 

 given figures, 2,291 and 2,749. But, as Mr. 

 Messenger rightly says, it is not so much the 

 average as the median that is here significant. 

 This was found to be 25, as compared with 45 

 for the Columbia students and 99 for the stu- 

 dents of the University of Kansas. 



Since a five-dollar gold piece is a relatively 

 unknown quantity to those of us who live in 

 this part of the country, a further question 

 was asked as to the number of one-dollar bills 

 requisite to equal in weight a fifty-cent piece. 

 The average of 162 replies was 161.7, the me- 

 dian 50. The correct number is between 9 

 and 10. Familiarity with the coin seems not 

 to have added materially to the correctness 

 of the estimate. 



I am not at all sure that such investigations 

 as this disclose any profound psychological 

 laws, but the results here given may serve to 

 correct the error that women are less capable 

 than men to make estimates of this sort. 

 A. H. Pierce. 



Smith College. 



a point in nomenclature. 

 More than once lately, lacking time to ex- 

 plain my views on zoological nomenclature in 

 detail, I have stated to correspondents that 

 they agreed with those of Dr. D. S. Jordan, 

 supposing the latter to be well known. I am, 

 therefore, somewhat distressed to find Dr. 

 Jordan and Mr. Fowler (Proc. U. S. Natl. 

 Mus., XXV., pp. 266-268) adopting a course 

 in nomenclature which seems to me inadvis- 



