404 Transactinns. — Chi'mistri/. 



maintains to be explanatory of these movements, is re-stated in a controver- 

 sial letter "which appears in the "London Chemical News."* This theory is 

 quite antagonistic to the one I advocated in the paper of mine referred to, as 

 it supposes these movements are due to a " difference between the tension 

 of water and that of the camphor solution at different points of the surface." 



I have also learned since the communication of this paper, that Mr. 

 P. Casamajor has read one before the American Chemical Society, in 1874, f 

 in which he ascribes these movements to electrical reactions, and in a letter 

 of his published in the ' ' Chemical ISl ews, ' ' I he attempted to sustain this theory 

 as against that of Professor Tomlinson. Along with this, I find that the 

 subject of camphor-movement has been one of great interest to the scientific 

 world since the year 1787, when Volta investigated it, followed by Carradori, 

 Dutrochet, Dr. Thos. Young, and, in 1862, by Prof, Van der Mensbrugghe. 

 A knowledge of this and of the more recent opinion of the two scientists 

 first named, has induced me to make further investigation respecting the 

 phenomena of camphoric movements, and the direction of which has, I am 

 happy to acknowledge, been given by information supplied by Mr. Casa- 

 major. 



Before I give the results of this further investigation of mine, I will just 

 say now what I have to say in respect to the rival theories which I have 

 described to you. 



In regard, first, to that of Mr. Casamajor, I have to inform you that I 

 tried to reproduce some of the results upon wdiich this is founded, and was 

 quite unsuccessful. One experiment, especially, I tried several times — that 

 where vulcanite electrically excited is applied to camphor which has been 

 rendered stationary upon water by a glass-rod, and I entirely failed to set 

 the camphor going. When one considers the effect which a minute portion 

 of greasy matter has in arresting this kind of motion, one cannot avoid 

 thinking that the unrecognized interference of such matters in Mr. Casa- 

 major's experiments has vitiated the value of their results and so led him 

 a little astray. 



As regards Professor Tomlinson's "tension" theory, I cannot go over 

 the evidence upon which it rests, as I am unable as yet to possess myself of 

 it ; nor again can I examine the mode in which he makes the difference of 

 tension described to result in camphor movement, as I have only a know- 

 ledge of the bare assertion itself, being, as I have said, unable to obtain the 

 essay referred to. 



Pending, therefore, the receipt by me of full and definite information of 

 this kind, I must for the present forbear from any direct examination of the 



* Vol. XXXYI., p. 937. t " London Chemical News," Vol. XXXVI., p. 191. 



I Vol. XXXVI., p. 285. 



