268 Defcriptlon of the differ e?it Methods 



^deration of the Imperial Parliament, which, after examining 

 various documents, and hearing the teftimony of feveral pro- 

 feffional men of the fird eminence, acknowledged the value 

 of the difcovery by voting a reward of io,cool. to Dr. Jenner. 



XLV. Defcriptlon of the different Methods of blowing vp 

 Rocks under Water, By A. Bail let, Infpeclor of 

 Mines*. 



I ft, J. H E operation of blowing up rocks, which the French 

 call tirage des mines, is not in general attended with much 

 difficulty, when the hole of the mine is pierced in dry compact 

 ground without any fiflure or cavity. When the ground is 

 cavernous or hollow, or when water oozes through its pores, 

 it becomes more troublefome, and requires particular care. 

 When it is neceflary to blow up rocks at the bottom of the 

 water the difficulties are increafed. In that cafe the ufual 

 proceffes muft be abandoned, and others mud be reforted to. 



2d, The method of blowing up rocks in the latter cafe is 

 little known,. and not much praclifed : it may, however, be 

 of great utility in many cafes, not only in the working of 

 mines, but in the execution of public works of importance. 

 Thei'e motives have induced me to give a defcription of the 

 three principal methods of blowing up mines under water. 



The firft is that ufed in the mines in the northern part of 

 the republic : it is proper to be reforted to when the depth 

 of the water which covers the ground intended to be blown 

 up is not above 15 or 18 decimetres. 



The fecond has a great refemblance to the procefs ufual 

 in mines when the ground futTers the water to ooze through 

 it. It is fimpler ancl lefs expenfive than the preceding, and 

 appears to me to be very proper for cafes when there are only 

 a few decimetres of water above the ground. 



The third is fuited to great depths of water, fuch as 4, 5, 

 or 6 metres: it is that employed at Carlfcrona. It is very 

 ingenious, and feems hitherto to have been unknown to 

 the French miners. 



31} , But, before I begin to defcribe thefe methods, it 

 may be of fome ufe to mention here an interefting memoir, 

 printed in the Journal de Phyfique for the year 1779, on the 

 conftrudtion of air-boats proper for facilitating the execution 

 of all forts of works under water, without employing pump* 



* From the journal des Mines, No. 56. 



ing. 



