EXPLOSIVES 177 



1% inches in diameter, each stick weighing half a pound. 

 Each cylinder is wrapped in paraffin paper to keep out 

 moisture and packed in boxes holding from five to one 

 hundred. Dynamite is manufactured in many strengths 

 or grades directly dependent upon the percentage of nitro- 

 glycerin present, which varies by steps of 5 per cent from 

 20 to 70. The smaller the nitroglycerin content, the slower 



fell A 



After E. I. du Pont de Nemours & Co. 



Fig. 156. Stick of dynamite 



and less shattering the explosion. Grades varying from 

 25 to 40 per cent are the ones best adapted to work on 

 the farm. 



Dynamite may be fired by a severe concussion or blow, 

 its sensitiveness increasing with the temperature. When 

 brought close to a flame in the open air it will take fire at 

 356 Fahrenheit and burn slowly, but if confined it may 

 be exploded by a red-hot iron or by being heated to a high 

 temperature. While dynamite can be safely handled at 

 ordinary temperature, it decomposes when exposed to the 

 direct rays of the sun, and it is dangerous to allow the sun 

 to shine upon it through a window. In water the nitro- 

 glycerin separates from the base, and for that reason in 

 wet places it should be fired within one-half hour after 

 being placed. The absorption of moisture decreases its 

 strength, 15 per cent being sufficient to prevent explosion. 

 It freezes at a temperature of 42 ° to 50 Fahrenheit. 



Advantages of dynamite. For use on the farm dynamite 

 has many advantages over black powder. It is in more 

 convenient form, produces better results, is safer, and per- 

 mits greater economy of time and labor. Since it is manu- 

 factured in so many grades, one can be found suitable for 

 practically any class of work in hand. It can be used under 

 conditions of moisture which would make black powder 



