Dr Turner on the Cyanuret of Mercury, fyc. 245 



After all ray care, the delicacy of these observations is such, 

 that I do not feel myself entitled to give the true maximum 

 with so much precision as I had hoped ; but I feel confident 

 that it was above 84°, and state without hesitation, that in 

 perfect shade, and free from all usual defects in observation, 

 such as the proximity of buildings, errors in the height of the 

 mercury, &c. it was between the degrees 83 and 84. 



The temperatures in the sun cannot be perfectly trusted to 

 perhaps within 1°; the bulb of the instrument was covered 

 with black woollen stuff. The wind was variable throughout 

 these experiments, and cirri, cirro-cumuli, and cumuli, slight- 

 ly prevailed. 



The following days were very warm, but not so remarkably 

 as the above. On the 27th was a thunder-storm, in the middle 

 of which I took the temperature of a spring, which was no 

 higher than I had reason to believe, from my observation of 

 the day before on the same spring. This does not confirm 

 the conjecture mentioned in the last number of the Journal of 

 Science. 



P. S. — Some have stated that few and small solar spots in- 

 dicate hot weather, and others the reverse. On the 17th 

 June, while the weather was quite cool, and I was not think- 

 ing of such coincidences, I found a spot coming on the sun, 

 which I have stated in my memorandum to be an " immense 1 * 

 one. Indeed, it was almost the largest I ever saw, and I took 

 a sketch of it. It was approaching the sun's western limb on 

 the 24th. This appears to favour the latter hypothesis. 

 July 1826. A 



Art. XI. — On the formation of the Cyanuret of Mercury, and 

 the Sulpho-cyanate of Potash. By Edward Turner, M.D. 

 F.R.S.E. Lecturer on Chemistry, and Fellow of the Royal 

 College of Physicians, Edinburgh. 



The directions contained in systematic works on chemistry for 

 the formation of the cyanuret of mercury, appear to have been 

 derived from Proust's excellent paper on Prussian blue, pub- 

 lished in the 60th volume of the Annates de Chimie. M. 

 Thenard directs that two parts of good Prussian blue, in fine 



