1 34 Blasting of Rocks — Dangers and Remedies. 



11. Letter of Mr. Blake. 



Whitncyville, September 5, 1829. 



TO PROF. SIJLLIMAN. 



My dear sir — In blasting rocks, as you know, it is not an uncora- 

 raon thing for explosions to take place before the charging is completed. 

 Almost every year some of our numerous newspapers give accounts 

 of such premature explosions, attended with fatal consequences to the 

 operators. The cause of the accidental ignition of the poAvder in these 

 cases, is sometimes clearly indicated by the known circumstances of 

 the case, and at others it can only be referred to the unknown circum- 

 stances, which may have attended the operation. I have read with 

 attention the letter on this subject, which you did me the honor to 

 refer to me, which was addressed to you by Dr. B. H. Catlin, of 

 Haddam, giving an account of an accident of this kind, and soliciting 

 information as to the cause of the ignition of the powder and the 

 means of avoiding similar accidents in future ; and shall now with 

 pleasure proceed to state to you my views of the subject, as you 

 desired. 



The method of charging the rock in this case, as minutely descri- 

 bed by Mr. Catlin, was that which is now most generally practised, 

 and it is perhaps the only method that was in use twenty years since. 

 The workman appears to have used more than tlie ordinary degree 

 of caution ; and I cannot see that there was any thing in the case to 

 produce explosion, which is not liable to exist, in every case, in which 

 this method of charging is practised. In the Journal of Science, 

 Vol. XIII. p. 161, are given the results of some experiments tried by 

 M. Aubert, which go to show that violent shocks and percussions, 

 between any two hard substances, may occasion the disengagement 

 of sufficient heat to inflame gunpowder ; and it is well Icnown that 

 violent attrition is still more favorable to the disengagement of heat 

 than percussion. To both of these the process, as described by Mr. 

 Catlin, is evidently in some degree liable. In tamping down the first 

 quantity of gypsum, which was put in next above the wad, the irreg- 

 ular pressure of those pieces which were in contact with the wad, 

 would be very liable to force tlie wad down on one side of the hole 

 or in the centre, which would cause the powder to be throwii up on 

 the odrer side or on all sides. The spindle is usually inserted into 

 the powder on one side of the hole ; consequently tlie Avadding would 

 not be likely to close the hole entirely around the spindle, and the 



