1819.] Scientific Intelligence. 231 



In going to Tivoli, I used a similar guard with advantage when 

 passing the brook flowing from the " Lago di Tartaro," the 

 odour of which is almost insupportable. 



The use of crape, &c. is evidently to guard the eyes from the 

 pain of reflected light, and the merits of wire gauze in the safety 

 lamp for miners depend on its cooling powers. The gauze veil 

 in the case suggested acting as a screen or Alter, would oppose 

 the passage of humid air, and with it the elements of contagion, 

 whatever they may be. I found that breathing on the rings of 

 Breguet's metallic thermometer moved the index to the left from 

 zero (marked " tempere ") to 15° + • but when I repeated the 

 experiment through a silk screen,, it scarcely reached 12°. 

 I have the honour to be, Sir, 

 Your most humble and very obedient servant, 



J. Murray. 



VI. Evolution of Carburet ted IL/drogeu Gas from Coal. 

 By Mr. Murray. 

 Mr. Longmire ascribes the formation of carburetted hydroo-en 

 in mines to the high pressure under which coal was formed ; and 

 Sir H. Davy reiterates the same opinion. This assumption, how- 

 ever, is evidently hypothetical. Mr. Hodgson has clearly moved 

 that when coal is broken under water, carburetted hydrogen is 

 disengaged. Now it is a well known fact, that this gas obtains 

 in greatest abundance in the vicinity of dykes which abrupt the 

 coat. It appears to me, therefore, very evident, that these dykes 

 by dislocation of the strata and crumbling the coal, for we know 

 that this is palpably the fact in coal connected with faults, are 

 the effective cause of disengaging the fire-damp. 



VII. Pus of Venereal Sores. 

 M. Chevallier has published the result of a set of experiments 

 to determine the constituents of the pus obtained from venereal 

 sores. We are afraid that such experiments are not likely to lead 

 to any consequences of much importance. Pus, in all probabi- 

 lity, is of the same nature when laudable, whatever has occa- 



ned the abscess from which it was extracted ; but when the 

 ulcers are ill-conditioned, the appearance of the pus is much 

 altered, and its constitution in all probability changed. It would 

 be a material point to determine the nature of this alteration. I 

 BUSpecl hum the facts which have been recorded by observing 

 surge, ms, that in certain cases ill-conditioned pus is alkaline* 

 while in others it is acid. The pus from venereal sores, espe- 

 cially when the constitution has been broken down by the 

 excessive use of mercury, is frequently ill-conditioned, and it 



mis to be always more or less alkaline, and the alkali is always 

 ammonia. Its smell is often fetid, and one would be tempted to 

 suspect that it has undergone a kind of putri faction. 



Some of the ulcers from which the pus subjected by Cheval- 



