Hi. L. Abbot—Transmission of Earth Waves. 183 
the later observations at Willet’s Point; and have thus an- 
swered this argument which, when the results were first col- 
lated, suggested itself to my own mind. 
. Mallet next mentions certain objections that show him 
not quite to understand the geography and geology of the 
region separating Hallet’s Point from the four stations; which, 
in the absence of a map to illustrate the paper, is very natural. 
The straight line to Willet’s Point follows the shore and waters 
of East River, offering both a land and water route to the 
wave of disturbance. The other three stations lie in the in- 
terior of Long Island, with no water between them and Hallet’s 
Point. The intermediate country consists of low rolling hills 
formed of deposits of the clay, sand and boulders characteristic 
of drift, the geological formation to which they belong. The 
rated : 
rock, (3) by the fall of the water; and also to the wave-diffu- 
sion experienced in traversing long distances. He argues, 
therefrom, that the distances were too great for satisfactory 
ati Now the records show both the beginning and 
end of the mercury vibration, as well as the automatic signal 
sent by the explosion. The first and last determine the veloc- 
