156 Scientific Intelligence. [Aug. 



Museum, a specimen of chalk from a pit in Kent, containing a 

 vein of fibrous limestone. Dr. Leach had himself observed the 

 vein in the chalk, and had brought away the specimen. The 

 thickness of the vein was about half an inch, and the fibres, as 

 usual, ran across the vein. They were fine, nearly as much so as 

 those of satin spar; but they were destitute of the lustre which 

 distinguishes that variety of fibrous limestone. Tts colour is yel- 

 lowish white; lustre, glimmering. It has not in the least the 

 aspect of calcsinter. \et the most probable opinion that suggests 

 itself to me respecting its formation is the occurrence of a rent in 

 the chalk, which was gradually filled up by the crystallization of 

 limestone from the water which had made its way through the 

 chalk ; for I consider the fibrous form, which limestone veins occa- 

 sionally assume, as the consequence of crystallization. 



On subjecting this fibrous limestone to analysis, I found its com- 

 position the same as that of common carbonate of lime. 



IV. Electricity from Cloth. 



(To Dr. Thomson.) 

 SIR, 



On the 6'th of March, 1813, I was accidentally left in the dark 

 in the place where the calendar of Mr. Richard Hilton, of Dauven, 

 was at work. I observed a very large quantity of electric fire (so 

 much so as ,o illuminate tiie piece) generate ■ at the place where 

 the cloth parted from the paper cylinder ; and I afterwards procured 

 sparks in great plenty by the friction of the cloth in passing over 

 some beech staves previous to its entering the calendar; but here it 

 '.: rv c ssary to damp the piece. The calendar has five cylinders: 

 three ot paper, and two of iron, one of which was heated at the 

 time 



As I have not since had an opportunity of observing these appear- 

 s, von will oblige me by inserting this note (if you think if 

 deserves a place) as" an incitement to some of your friends who 

 have an opportunity to pay a little attention to them. 



I am, Sir, yours respectfully, 



\ Spring Gardens, Preston. VVm. Gl LBERTSON. 



V. Sudden Change of Temperature from Ram. 



From the theory of latent heat one would he disposed to expect a 



of temperature from t'ie falling of rain ; or, at any rate, we 



<id not expect a sudden production of cold in consequence of 



the occurrence of a shower of rain. On that account 1 consider 



the following occurrence as worth recording. 



On the 25th of May, 1813, the thermometer in London at half past 

 nine in the morning stood at 60°. Soon after, a heavy shower of rain 

 fell from the west, and lasted half an hour. During its continuance 

 the thermometer sunk rapidly to f,0° ; and during the wholeday 

 never gamed its original height at half past nine in the morning; 

 for it rose no higher after the rain than 58°. 



