EXPLOSIVES AND ELECTRIC BLASTING CAPS 
FOR GEOPHYSICAL PROSPECTING 
G. H. LOVING and G. H. SMITH! 
INTRODUCTORY REMARKS 
In the early days of seismograph explorations, the explosives and 
electric blasting caps were of the same design as those supplied for 
ordinary types of blasting. During the succeeding years, the instru- 
ments and shooting practices employed in geophysical prospecting 
were constantly improved with the result that the usual products of 
the explosives manufacturers failed to satisfy the highly specific re- 
quirements of this kind of work. It is the purpose of this paper to 
present the pertinent characteristics of the special types designed for 
the seismograph trade and to enumerate the more important steps 
taken during the development program. For the sake of clarity, the 
data on explosives and electric blasting caps will be given separately. 
EXPLOSIVES FOR GEOPHYSICAL PROSPECTING 
Before mentioning the properties and physical characteristics of 
the explosives now used in seismograph work, the factors, influencing 
the development of the special types brought out for the geophysical 
trade within the last few years, will be reviewed. It will be under- 
stood, of course, that the discussion applies only to exploration work 
as carried on in the United States. 
Several years ago, the refraction method of prospecting was the 
‘accepted type. With this procedure, the explosives employed to 
initiate the seismic wave were stacked on the surface of the ground, 
sometimes as much as several thousand pounds of powder being used 
per shot. The geophones for recording the earth vibrations were 
placed on the arc of a circle several miles distant from the shot point. 
Since the dynamite was not loaded in holes or under water and, in 
many instances, not even removed from the boxes, the only pre- 
requisite was that it detonate with the desired velocity. Later modifi- 
cations included the use of shallow holes, dug by hand and loaded with 
large diameter cartridges, using water tamping, or well-drilled, water- 
filled holes into which the explosive was loaded by means of tin tor- 
1 From the Eastern Laboratory, E. I. du Pont de Nemours & Company, Gibbs- 
town, N. J. 
27 
