and Attached Water. 113 



convenient term to apply to the cause of the increased period 

 of oscillation which such association entails ; but, of course, 

 any systematic obstruction to vibration, any drag, would have 

 the same effect as the drag of inertia. 



§ 190. In some experiments relating to the " wandering of 

 the ions " in jellies during electrolysis, which I had the honour 

 of bringing before the Physical Society on the 16th of March, 

 1878, I described the spreading of the acid and alkaline ions 

 through the unmelted jelly. These results I clo not publish, 

 because a friend has had the great kindness to point out to me 

 that many of the results which were then exhibited had been 

 obtained several years previously by Dr. W. M. Ord. The 

 experiments and speculations of Dr. Ord are contained in a 

 very remarkable and suggestive series of papers contributed 

 chiefly to the St. Thomas's Hospital Reports *. Amongst the 

 jellies which I then prepared but did not exhibit, was a stiff 

 gelatine jelly saturated with sulphate of copper. This jelly 

 was of a bright emerald-green by transmitted light. On ex- 

 posure to the air of a portion which had not been subjected 

 to electrolysis, the water gradually evaporated and the salt 

 began to crystallize out. The form of the crystalline masses 

 was curiously modified by the jelly. Rounded masses were 

 formed, reminding one of my friends of the coccoliths of the 

 deep-sea dredgings — another, of the mineral or uric concretions 

 which occur in mucous media — and yet another, of "chlorite." 

 Whether there be, as is most likely, a common cause, a colloid 

 medium, in all the three cases, I must not here discuss. The 

 ultimate crystalline element is too minute for determination; but 

 the elements of secondary form invariably re- 

 semble (1). These elements are frequently 

 linked two by two in one plane (2), or at right 

 angles to one another (3). The convex sides 

 are generally very deeply furrowed, so as to 

 give the impression of their being four second- 

 ray elements. These concretions can be picked 

 out of the jelly in which they form, like 

 almonds out of a cake. So clean is their se-' 

 paration, and so feeble their blackening when 

 heated with oil of vitriol, that they must be 

 regarded as homogeneous bodies free from 

 gelatine ; and their composition is therefore 



* " Some Experiments relating to Forms assumed by Uric Acid " (St. 

 Thomas's Hospital Reports, 1870); "An account of some Experiments 

 relating to the Influence exercised by Colloids upon the Forms of Inoro-anic 

 Matter" (St. Thomas's Hospital Reports, 1871) ; " Studies in the Natural 

 History of the Urates " (Rep. Microscopical Society, Jan 6, 1875); "On 



Phil. Mag. S. 5. Vol. 6. No. 35. Aug. 1878. I 



