ON HOLIDAY IN EDINBURGH 65 



SOMERSET COTTAGE, 

 COMELY BANK, 



EDINBURGH, 21/7/59. 



My dear Dr Andrews, 



I was very glad to find from your letter that you had been successful in 

 procuring apparatus in London.... 



I did not expect more from Faraday than you seem to have obtained, for I 

 thought it scarcely possible that he could suggest at an hour's notice anything that 

 we might have missed for three years. 



My paper on the Wave-surface has reached me in separate form and I have 

 been asked by several men of note, to whom I have sent copies, to publish an 

 elementary work on Quaternions. Todhunter of Cambridge, about the best authority 

 on matters of that sort, is one of them and I have written to Macmillan (the 

 publisher) to enquire about terms etc.... 



Sir W. Hamilton has expressed his satisfaction with the project and has only 

 asked me to refrain from laying, or trying to lay, new metaphysical or other foundations 

 for the Theory, wishing to reserve such for himself; and I am quite sure that I 

 shall not feel this in any way a restraint.... 



I have ordered the addition to the small electrical machine.... There is only one 

 novelty here, so far as I can see, and as it is extremely interesting, I have given 

 an order for one. Its object is the compounding of colours by rapid rotation, and 

 so far it is simple but when used in combination with a looking glass (like the 

 Thaumatrope) it gives some most startling but easily explained and instructive 

 effects.... 



SOMERSET COTTAGE, 



COMELY BANK, 



EDINBURGH, 18/6/60. 



My dear Andrews, 



I shall probably leave this for Cambridge on Monday next, and it will not be 

 possible for me to be in Oxford as Hopkins and I are to be engaged in getting up 

 our Ex n Papers just at the time of the Ass n Meeting.... 



Dr Bennett showed me on Saturday the whole series of frog experiments with 

 a splendid galvanometer from Berlin and German Frogs which he had imported ! 

 But what interested me most was the perfect success of the experiment showing the 

 muscular current in the operator himself, that you remember which we could not 

 repeat and had begun to doubt. Mr Pettigrew, his assistant, produced by contracting 

 his right arm a deflection of 15 E., then by contracting his left arm, one of 35 W. 

 50 in all. Neither Dr B. nor a Russian who was present could produce more than 

 very uncertain results. I no longer entertain any doubt as to the reality of the 

 phenomenon. The explanation, however, does not seem quite satisfactory. Dr B. told 

 me that Humboldt had skinned his forefinger by raising blisters in order to get rid of 

 the great resistance of the skin, and that then he produced extraordinarily great 

 deflections.... 



T. 9 



