Blasting of Rocks — Dangers and Remedies. 135 



powder would be therefore, particularly liable to be thrown up around 

 the spindle. By proceeding with the tamping, this powder would be 

 brought in close and hard contact with the spindle, and in withdraw- 

 ing the spindle in the manner mentioned by Mr. Catlin, would be 

 subjected to violent attrition, between the spindle and the gypsum or 

 between the spindle and the rock. Whether this was or was not the 

 precise cause of the explosion, cannot perhaps be determined ; nor 

 will it be important to know, if, without this knowledge, satisfactory 

 information can be given in regard to the manner in which the recur- 

 rence of similar accidents may be prevented in future. 



About twenty years since another method of charging a blast was 

 proposed and circulated in the newspapers, which, since that time, has 

 been practised to some extent in different parts of this country. This 

 method may be briefly described as follows, viz. After putting in 

 the powder, take a rye or wheat straw, which is long enough to reach 

 from the powder to the top of the hole, and having filled it with 

 powder, insert one end of it into the charge ; after which put in a 

 small quantity of wadding, and then fill up the hole with coarse dry 

 sand, simply poured in without any ramming. 



When about ten years since my attention was turned to blasting, I 

 made a trial of this method, with great success in some cases but 

 without any effect in others. I soon found that when the hole was 

 deep, the effect was not only certain, but also more powerful than 

 when charged in the old method. But when the hole was shallow, 

 the sand would generally be thrown out without producing any effect 

 on the rock. When the depth of the sand above the powder is not 

 less than ten times its diameter, I have never known it to be thrown 

 out. In all such cases therefore, I can from experience recommeild 

 this method as one which is perfectly safe and sure, and at the same 

 time more expeditious and more effectual than the old method. 



Since my attention has been drawn to this subject by Mr. Catlin's 

 letter, an equally safe method has occurred to me, of securing a blast 

 in holes of less depth. This method is as follows ; viz. Having put 

 in the powder, and inserted into it, on one -side, the straw filled with 

 powder, as directed above, put in a small quantity of wadding and 

 press it compactly down ; then make a cone of wood, the diameter 

 of whose base is a little less than the smallest diameter of the hole, 

 and whose height is a little less than the distance from the top of the 

 wad to the top of the hole. Set the base of this cone on the wad, 

 and then keeping the vertex in the centre of the hole, fill in around 



