^C4 0/? the Presence of Fluoric Acid 



powerfully ventilated ; for it is without doubt that they are 

 invariably generated by the same process and at the same 

 time." 



Such are the means proposed by Dr, Trotter for destroy- 

 ing the Jirc- and choak-damps in coal mines. The ingre- 

 dients, he observes, are so cheap, that " the largest mine 

 could not consume one hundred pounds (value, we suppose, 

 henienns,) in the year, by keeping the fumigation in con- 

 stant use day and night." But the constant use of it would, 

 we think, be impracticable ; for too free an inhalation of 

 oxy-rauriatic acid gas is apt to produce pleurisy, and many 

 people fcll'victims to this malady in dltferent' works when 

 this gas ^^•as first introduced for the purpose of bleaching. 

 The intention of the author is, however, not ihe less praise- 

 worthy ; nor should this oversight militate against a fair 

 trial, judiciously conducted, of the means he has suggested. 

 We believe few or none of the mines are worked in the 

 night-time. Before quitting the mine the fumigating pans 

 might be properly disposed, and the desired end probably 

 be gained before the people return to their work in the 

 morainw;. 



LII. jLe/'/e.'-.()/' i\/. Gav-Lussac /o 3/, Berthollet, o/t 

 the Presence of Fluoric Acid in Animal Sutsia7ices*. 



My honoured friend, 



W HEN I quitted Paris, about four months ^o, you were 

 at that time unacquainted with the existence of fluoric acid 

 in animal substances; and I have since received from you" 

 no notice of that beautiful discovery. I conceive, there- 

 fore, that you will be gratified by the communication of 

 what I have learnt respecting it from M. Morichini, a Ro- 

 man chemist, by whom this discovery was mnde. As it 

 was announced by him so early as the year 1802, you will 

 no doubt be astonished that it should have remained so long 

 unknown in France, and excited so little the attention of 

 chemists. 



In April 1802 the skeleton of an elephant was found in 

 •the neighbourhood of Eome, an account of which has been 

 published by count Morozzo in the Journal de Phj/sirjne of 

 Paris. The dcn/es molares of this fossil elephant are formed 

 of two very distinct substances; the inner of these is os- 



» Froia the Ar.nalts de Cliimie, No. 165. 



seous. 



