Under g round of Paris. 159 



and weight of the air. Certainly, however, it was colder 

 at this time than on the surface of the earth. But Mr. 

 Smeathman informed me, that when he descended the last 

 winter in the long and hard frost he found the air much 

 more temperate than above ground, but far from warm. 

 Neither, however, had he a thermometer with him. I 

 lamented too that I had not time to make more remarks 

 on the petrifactions, &c. 



* Mr. Smeathman observed, that when he descended, he 

 found a very sensible difficulty of breathing in some of the 

 passages and caverns, where the superincumbent rock was 

 low, and the company crowded. This no doubt was much 

 increased by the number of persons and of wax lights, but 

 he does not apprehend that the difficulty would have been 

 so great in rooms, of equal dimensions above ground. 

 We remarked too, when we descended, that there was, in 

 some degree, an oppression of respiration throughout the 

 whole passage. 



'There were formerly several openings into the quarries, 

 but the two I have mentioned, viz. the Observatory and 

 the Val de Grace, are, I believe, the only ones left ; and 

 these the inspectors keep constantly locked, and rarely 

 open them, except to strangers particularly introduced, 

 and to workmen who are always employed in some part by 

 the King. 



' The police thought it a necessary precaution to secure 

 all the entrances into this cavern, from its having been 

 formerly inhabited by a famous gang of robbers, who 

 infested the country for many miles round the city of 

 Paris. 



' As to the origin of this quarry, I could not, on the 

 strictest inquiry, learn anything satisfactory ; and the only 



