RAILROAD CONSTRUCTION 307 
suitable for very hard rock or where snuill (h'ill holes are necessary. 
Medium grades are best for soft rock because their explosive 
force is not so violent and sudden, and the tendency is to heave 
up large masses of rock rather than to shatter them into smaller 
fragments. 
Dynamite which is rather soft resembles brown sugar. It 
is packed in paraffine coated paper shells or cartridges, the stand- 
ard size being If by 8 inches and containing one-half pound. 
Other sizes, from |-inch to 2 inches in diameter and 6 inches and 
over in length are also manufactured. Dynamite cartridges are 
packed in sawdust in wooden boxes containing 25 or 50 pounds 
each. 
Dynamite freezes between 38 and 55 degrees Fahrenheit and 
w^hen frozen must be thawed before use. Thawing kettles which 
are best for this work consist of a double galvanized iron bucket 
having an inner water-tight receptacle for dynamite and an outer 
receptacle for warm water which must not exceed 100 degrees 
Fahrenheit, otherwise the nitro-glycerine may separate from the 
absorbent. Cartridges are sometimes spread out on a shelf in a 
warm room and left during the night but should never be thawed 
in an oven, near a fire or placed against a stove or steam pipe. 
A few cartridges can be easily thawed out by placing them flat 
in a water-tight box and burying them in fresh manure. 
Some of the low-freezing dynamites will not freeze above 32 
degrees Fahrenheit, while the so-called Trojan powder is practically 
non-freezing. Nitro-glycerine evaporates rapidly at 158 degrees 
F. and at 104 degrees F. dynamite may lose as high as 10 per 
cent of its nitro-glycerine in a few days' time. Because of the 
tendency of nitro-glycerine to freeze in cold weather and to 
evaporate in warm weather dynamite should be kept in a warm 
place in winter and in a cool place in summer. 
Great care must be taken to prevent the dynamite from coming 
into contact with moisture, because water has a greater affinity 
for the absorbent than has nitro-glycerine, and the latter wall be 
driven out; on low grades of dynamite the salts of the auxiliary 
explosives are also expelled. 
Dynamite which contains impure nitro-glycerine deteriorates 
during warm weather, when stored in a warm place, or if kept 
for long periods. Chemical decomposition takes place, liberating 
nitrous fumes which often are the cause of violent explosions. 
