178 H. L. Abbot—Transmission of Earth Waves. 
Art. XXIIL—On the Velocity of Transmission of Earth Waves ; 
by General H. L. Assor, Corps of Engineers. 
ADVANTAGE was taken of the explosion of 50,000 pounds of 
dynamite at Hallet’s Point, on September 24th, 1876, to meas- 
ure the velocity with which the shock was transmitted through 
the ground, both across Long Island and along the south bank 
of Kast River. The results were embodied in a paper read by 
me before the National Academy of Sciences, on October 18th, 
1876, and subsequently again read and printed as one of the 
papers of the Essayons Club of the Corps of Engineers. 
n the number of the London, Edinburgh and Dublin Phi- 
losophical Magazine, for October, 1877, appeared a short review 
of this paper from the pen of Mr. Robert Mallet, F.R.S., a gen- 
tleman well known for his numerous and able contributions to 
seismology. In this article, he suggested reasons which | 
him to doubt the value and accuracy of the Hallet’s Point 
resu 
Even if I had felt disposed to enter into a controversy upon 
the subject, 1 should have been quite disarmed by the conclud- 
ing sentence of this article, which expresses views so just an 
liberal that it may well be quoted as an exemplar of the man- 
ner in which scientific questions should be considered. He 
writes : 
“Tn these objections I wish to be clearly understood as hav- 
ing no a priord difficulty in accepting a higher velocity of wave 
transit than the highest attained experimentally by myself. It 
is highly probable that such may be elicited by future experi- 
‘ment. But should such cases arise, their results like all great 
physical truths, should only be credited upon unexceptionable 
observations or experimental evidence. While feeling justi- 
fied in making these objections, I wish to disclaim all contro- 
versial spirit or intention; loss of sight, indeed, and diminished 
energy would prevent my engaging in any scientific contro- 
versy, were any called for.” 
Believing, at the date of my first paper, that the data secured 
at the Hallet’s Point explosion demonstrated the necessity for 
more exact and comprehensive knowledge of the subject, I 
have, during the past season, taken advantage of the facilities 
offered by large sub-aqueous explosions at the School of Sub- 
marine Mining at Willet’s Point, to continue the investigation ; 
and, on October 23d, 1877, I read a second paper before the 
National Academy of Sciences, giving the results thus obtained. 
As only a brief abstract of this paper has appeared in print, I 
ropose now to give a summary a ie conclusions suggested 
y the whole series of experiments and, incidentally, to explain 
