Earth Vibrations Caused by Quarry Blasting.--What should be of unusual interest to geophysicists and others is the U. S. Bureau of Mines Progress Report I on this subject, known as Report of Investigations 3353 by J. R. THOENEN and S. L. WINDES. This paper outlines briefly results of seismic measurements recorded in the vicinity of quarry blasting under practical operating conditions. The data cover field work done from January to the middle of August 1936 , during which time records were made of 61 blasts in 19 quarries. Of the tests made one was in biotite-gneiss, two in dolomite, two in a flintlike volvanlc complex, three in gabbrodiorite, five in trap rock, and six in limestone. With seismometers set at the same locations as some of the blasts, two attempts were made to record the vibrations transmitted by railroad trains. Also four tests were made to record vibrations imposed upon a building by mechanical impact. The results indicate that if the amplitudes are plotted against distance for the explosive charges, for comparable distances and charges the amplitudes on outcrop are generally one tenth to two thirds that on overburden. Because of geologic differences a general mathematical formula of the relation between amplitude, distance, and explosive charge can only be approximate and the variation between the observed amplitudes and those computed from a formula will be as much as, if not greater than, the variation between amplitudes or overburden and outcrop at a particular distance and charge. A study of the observed frequencies of vibration indicates that there were no outstanding vibrations that could be attributed to the variation in type of rock. In summarizing vibrations in buildings it is noted that the excitation may be of two types--vibration produced through coupling with the ground and vibration produced through impact of air on the structure. In the immediate vicinity of the blast the compressional wave or air disturbance travels at high speed, which is greater than the speed of sound and which is attributed to actual displacement of air rather than a vibratory wave passing through it and leaving it relatively undisturbed, as is the condition when a less violent shock occurs. The predominance of the horizontal vibrations in buildings resulting from the air blast indicates that the observed motion was not floor motion alone, which probably would be largely vertical, but represented movement of the whole structure horizontally. R. H. O.