Decembek 21, 1917] 



SCIENCE 



617 



buzzing sound, "which seems to have been 

 simultaneous with the appearance of the 

 light. This communication is prompted chiefly 

 by a desire to learn if such sounds have been 

 previously reported as being connected with 

 meteoric falls. Several circimistances in the 

 present case indicate that this sound was real, 

 and not psychological. May it have been the 

 indirect result of some form of electric 

 energy? One observer seems to refer this 

 soimd to objects attached to the ground. 



J. A. Udden 

 Austin, Texas, 

 October 22, 1917 



ON THE COLLOID CHEMISTRY OF 

 FEHLING'S TEST 



To THE Editor of Science: Fischer and 

 Hooker make the following statement in their 

 article "On the Colloid Chemistry of Feh- 

 ling's Test," page 507, Science: 



Formaldehyde reduces Fehling's solution not 

 only to the ordinary cuprous oxide, but to the 

 metallic copper. The copper comes down in col- 

 loid form, but as this happens, a second reaction 

 ensues in which the metallic copper acts upon the 

 formaldehyde and decomposes it with the libera- 

 tion of hydrogen. The liberation of hydrogen con- 

 tinues for hours, until either all the formaldehyd* 

 has been decomposed or all the copper salt has 

 been reduced. 



In a study on the preparation of colloidal 

 gold solutions by Dr. J. H. Black and myself 

 (which is being reported by Dr. Black at 

 the present meeting of the A. M. A. at New 

 Tork), question arose regarding the probable 

 explanation of the mechanism by which neu- 

 tral sols are obtained although distinctly al- 

 kaline (to alizarine) sols should result from 

 the proportions of reagents employed. I sug- 

 gested the hypothesis that the colloidal gold 

 acted as a catalytic agent to oxidize the free 

 formaldehyde to formic acid, which latter 

 reacted with the potassium carbonate respon- 

 sible for the alkalinity. 



It occurs to me therefore that it would be 

 better to picture the colloidal copper fxmc- 

 tioning as a catalytic agent which oxidizes 

 the HCHO in part, the remaining part serving 

 to reduce the copper salt. The idea advanced 



by them that colloidal copper is produced is 

 certainly reasonable; it is very difficult to 

 understand how formaldehyde would liberate 

 hydrogen. Louis Eosenberq 



Department or Chemistry, 

 Baylor Medical College 



SCIENTIFIC BOOKS 



The Fundamentals of Botany. By C. S. 



Gager. Philadelphia, P. Blakiston's Sons 



& Co. 



We are fortunate in the United States in 

 having a number of excellent elementary bo- 

 tanical test-books, written from different 

 points of view. Professor Coulter has fur- 

 nished an admirable beginners' book conceived 

 from the standpoint of the head of a botanical 

 department in a large university, who is at the 

 same time an educational expert. From the 

 hands of Mr. Bergen, whose recent demise we 

 all deplore, we have had a succession of well- 

 approved texts, written by one thoroughly in 

 touch with instruction in the secondary 

 schools. Professor Ganong has put forward 

 from time to time books which reflect the 

 outlook of the teacher in college work. The 

 present volume comes from one who is the 

 director of one of the most important botanic 

 gardens in the country and who has, at the 

 same time, made it his business to get into 

 touch with his community, primary and sec- 

 ondary schools as well as the general public, 

 in the closest possible manner. There can be 

 little doubt, particularly at the present junc- 

 ture, when the general public under the spur 

 of patriotism and necessity, has largely aban- 

 doned its usual attitude of indifference 

 toward plants, that Dr. Gager's book will 

 prove extremely useful. 



The relation of the author to his subject is 

 admirable, as is shovm by the following cita- 

 tion (p. 192). 



... In fact, we may say that our ignorance of 

 life-processes greatly exceeds our knowledge. 

 "Very much more remains to be ascertained than has 

 already been found out; for example, what is 

 protoplasm? Nobody really knows. We have 

 analyzed the substance chemically, we have care- 

 fully examined and tried (but without complete 



