80 B. McCOLLUM AND F. A. SNELL 
TABLE III. Material: Tertiary sandstones, sands and clays. Shooting distance: 6000 meters. 
Station spacing: 500 meters. 



E Shots W Shots 
Stations Velocities Stations Velocities 
165-163 3290 127-129 3420 
163-161 2980 129-131 2980 
161-159 3120 131-133 3090 
159-157 3120 133-135 3050 
157-155 3050 135-137 2970 
155-153 3420 137-139 2990 
153-151 3380 139-141 2940 
151-149 3160 141-143 2910 
149-147 3050 143-145 3010 
147-145 3900 145-147 2600 
145-143 2940 147-149 3730 
143-141 3210 149-151 2870 
141-139 3290 151-153 3470 
139-137 3180 153-155 2910 
137-135 3080 155-157 3120 
135-133 3090 157-159 2980 
133-131 2930 159-161 3290 
131-129 3080 161-163 3160 
129-127 3080 163-165 3200 
127-125 3290 165-167 3330 
Average 3182 3101 

east, that is, away from the mountains, and would doubtless be steeper if 
investigated nearer the foothills. To illustrate this latter point we may 
average the western half of the group of velocities, Stations 125 to 147, with 
these results: East shot average, 3117 meters per second; West shot average, 
2996 meters per second; showing a greater difference than for the whole 
group. 
TABLE IV. Material: “Mottled clay”, Venezuela. Shooting distance: 500 meters. Station spacing: 


500 meters. 
E Shots W Shots 
Apparent velocities Apparent velocities 
2840 2480 
2870 2480 
2340 2500 
2530 2250 
2810 2290 
2400 2420 
2780 2170 
2600 2140 
Average 2646 2341 

Table IV shows the results of some scattered shots on two lines at right 
angles to the Perija Mountain front. The material is what is known as the 
“Mottled clay” of the Lake Maracaibo region. It is a compact clay with very 
224 
