23 



NATURE 



{Nov. 14, 1878 



rine and hydrogen when acted upon by radiations, but 

 that he also used it practically, though not with such 

 nicety of method as subsequently employed by Bun sen 

 and Roscoe. He also invented the ferric oxalate photo- 

 meter, dependent on the reduction of this ferric compound 

 to the ferrous state and the liberation of carbonic acid. 

 In both of the foregoing we have a measure of the 

 quantity of the radiations which these mixed gases, or 

 solution, select. On this particular subject of selective 

 absorption, when chemical action takes place. Draper ex- 

 perimented most fully. He showed, for instance, that the 

 sensitiveness of the surface of a Daguerreotype plate is at 

 its maximum when of a yellow tint, owing to the absorp- 

 tion of the blue rays, and conclusively shows that when 

 it is of a blue tint that these same rays are largely re- 

 flected. In fact, he announced, with all the authority of 

 -a successful experimentalist, that for the production of 

 •chemical action in a compound by any particular ray, 

 the absorption of that ray by the compound was an abso- 

 lute necessity. In late years we have had several redis- 

 coveries of this important truth, and probably it will be 

 rediscovered again and again, notwithstanding the publi- 

 cation of these memoirs. 



We have not space to do more than to mention the 

 memoirs on the " Distribution of Heat in the Spec- 

 trum," on "The Chemical Force in the Spectrum" 

 ^both titles of which, by the by, are inexact, as Draper 

 himself was the first to prove), and on " The Sup- 

 posed Magnetic Effects Produced by the Violet Rays," 

 all of which are important contributions to science, as 

 are also those on "The Cause of the Flow of Sap in 

 Plants, and the Circulation of the Blood in Animals," 

 and "On the Decomposition of Carbonic Acid Gas by 

 Plants in the Prismatic Spectrum." All .these have 

 been treated in a masterly manner, and the results 

 lucidly and tritely recorded. Reading these memoirs leads 

 tis to the conclusion that we have in Draper a successful 

 experimenter, who has been perhaps too little appreciated 

 in the world owing to his too great modesty in neglecting 

 to call attention to the facts he has observed, and to 

 claim for himself honour where the honour was due. 

 Xike other men of mark in science, the ardent pursuit of 

 it was undertaken through what might be termed an 

 accident. He tells us in his preface that happening 

 to see a glass containing some camphor, portions of 

 which had been caused to condense in very beauti- 

 ful crystals, he was induced to read everything he 

 could obtain respecting the chemical and mechanical 

 influence of light, adhesion, and capillary attraction ; the 

 experiments he made in connection with these subjects 

 being contained in the volume before us. His thoughts 

 being thus directed to physiological studies, he published 

 papers on these topics in the Aviericaii Journal of 

 Medical Sciences, which created such a favourable im- 

 pression that he was appointed, in 1836, Professor of 

 Chemistry and Physiology in Hampden Sidney College, 

 Virginia. He afterwards was appointed to a similar 

 chair at New York University, which, ^we believe, he at 

 present holds. 



It would be travelling out of our province to do more 

 than call attention to Dr. Draper as the author of *' A 

 Treatise on Human Physiology," " The History of the 

 Intellectual Development of Europe," "The History of 



the American Civil War," and of " The History of the 

 Conflict of Religion and Science," works which have met 

 with well-merited success, and which show the varied bent 

 of his mind. 



The history of the Rumford medal fund held in trust 

 by the Royal Society, and the awards made by this body 

 are too well known to need repetition ; but it is not equally 

 well known that a similar medal fund was founded in 

 the United States by Rumford, and is held in trust by the 

 American Academy of Arts and Sciences. The medals 

 were to be awarded for " the most important discovery or 

 improvement relating to light and heat that had been made 

 during the preceding two years in any part of America." 

 The awards of the American Rumford medals have been 

 made few and far between, and till 1876 may be said to 

 have been given for inventions rather than discoveries. 

 At this date the medal was awarded to Dr. Draper (as the 

 medal itself records) "for researches on radiant energy." 

 Had he been an European there can be little doubt but 

 that he would have received one of our English medals 

 years ago, and that his name would have been in the 

 same list with those of Leslie, Fox Talbot, Fresnel, and 

 Faraday. As it is he has the honour of being the first 

 recipient of the American Rumford medal which has ever 

 been awarded for pure scientific research. 



A CATECHISM OF BOTANY 

 A First Catechism of Botany. By John Gibbs, of the 



Essex and Chelmsford Museum. (Chelmsford: Edmund 



Durrant and Co. London : Simpkin, Marshall, and 



Co.) 

 This little book is in its way quite a curiosity. It is a 

 survival of a method of instruction which was very 

 popular in its day, but which it is to be hoped— notwith- 

 standing that Magnall's "Questions" is still said to be 

 a good property — even in country towns like Chelmsford, 

 is on the road to extinction. Catechisms originated in 

 the necessity of giving some uniformity and precision to 

 oral religious instruction. Their great merit is of course 

 that they remove all responsibility from the teacher, and 

 merely require that their formulas should be taught with 

 patience and perseverance. They render unnecessary, 

 indeed even undesirable, any knowledge of the subject 

 on the part of the teacher, and hence it is easy to see 

 the reason of their popularity amongst persons engaged 

 in education, and who, possessed of no scientific train- 

 ing, are yet anxious to get credit for teaching scientific 

 subjects. Mr. Gibbs has evidently felt some uneasiness f 

 on this head, and points out accordingly in his preface 

 that :— 



"The answer to every question may be verified by 

 examination of the plant itself in all its parts to which 

 reference is made. Only in such a way can this cate- 

 chism be made useful, and by such criticism its value , 

 will be ascertained ." ! 



But the insidious influence of the purely dogmatic method ■ 

 makes itself but too evident in the next sentence, which ; 

 is surely the strangest ground of recommendation ever , 

 urged for a scientific book : — 



"In its original form it was admitted to the Inter- 

 national Exhibition of 1871, which contained nothing! 

 but what the Committee of Selection approved as ex- 

 cellent." 



