156 Intelligence and Miscellaneous Articles. 



it, accompanied by a noise which made them think that one of our 

 shafts had crushed in, or runned together ; but on examining with 

 Capt. Crose, who was in the mine, we could find nothing at all amiss, 

 or any cause for the shock." 



This appears to be the most westerly part at which the tremor 

 was felt, and although the noise was heard away to the south, to- 

 wards the Lizard, it is clear it was much diminished in force. 



On referring to a geological map of the county, it will be found 

 that the greatest effects were produced near the edge of the granite 

 mass, which extends from the north-east to the south-west, from 

 Cam Marth to the south of Penryn. Although it was felt at Fal- 

 mouth, Helstone, and other places which are on the clay-slate, yet 

 all my inquiries go to show that it diminished rapidly in force, as 

 the distance from the granite increased*. 



A gentleman of Helstone says, " I felt it very sensibly, and my 

 house shook, but I experienced an effect on the sight which I always 

 find attends electricity ;" from which he appears inclined to deem 

 the disturbance as atmospheric. Had that been the case, it would 

 not have been felt in the mines ; but it is not improbable that a 

 manifestation of electricity may have attended this disturbance of 

 the earth. 



ON THE BLUE COLOUR OF ULTRAMARINE. BY M. ELSNER. 



According to all analyses hitherto published, ultramarine is com- 

 posed principally of soda, alumina, silica and sulphur, as shown by 

 the following statements : — 



Lapis Lazuli, 

 (Clement Desormes.) 



Soda 23-2 



Alumina 34-8 



Silica 35-8 



Sulphur 31 



Carbonate of lime . . 3*1 



Artificial Ultramarine of Paris. 4t1 ^ M V ^^ rnanufacture 



(C. G. Gmelin.) (Varrentrapp.) 



Soda (mixed with potash) 12-063 Soda 21*47 



Lime 1*546 Potash 1-75 



Alumina 22-000 Lime 0*02 



Silica 47-306 Alumina 23-30 



Sulphuric acid 4-679 Silica 45*00 



Sulphur 0-188 Sulphuric acid 3'83 



Resineus substance, sul- 1 lo.oia Sulphur 1'683 



phur and loss. J Iron 1-063 



* Mr. Hunt here adds some remarks on the condition of the atmosphere, 



and the heights of the barometer and thermometer at the period of the 

 earthquake. 



