At the Comstock Lode in Colorado about twelve years ago many earthquakes were felt. On one particular day twenty-four were counted. Superintendent Charles Foreman told the author when he visited Virginia City in 1882, that special observations were made to determine whether these shocks were felt as severely deep down in the mines as on the surface, where they were on the verge of being destructive. The universal testimony of many observers was that in most cases they were not felt at all underground, and when a shock was felt it was extremely feeble. At Takashima Colliery, in Japan, it is seldom that shocks are felt underground. The explanation of these latter observations appears to be either that, in consequence of a smaller amplitude of motion in the solid rocks beneath the surface as compared with the extent of motion on the surface, the disturbances are passed by unnoticed, or else the disturbance is, at a distance from its origin, practically confined to the surface. _Velocity of Propagation of an Earthquake._—Although many have written upon earthquakes and have endeavoured to give to us the velocity with which they were propagated, the subject is one about which we have as yet but little exact information. The importance of this branch of investigation is undoubtedly great. By knowing the velocity with which an earthquake has travelled in various directions we are assisted in determining the locality of its origin; we may possibly make important deductions respecting the nature of the medium through which it has passed; perhaps also we may learn something regarding the intensity of the disturbance which created the earthquake. In the Report of the British Association for 1851 Mallet gives the table on next page, in which are placed together the approximate rates of transit of shocks of several earthquakes which he discusses. Some of these, it will be observed, are records of disturbances which must have passed through or across the bed of the ocean. In Mallet’s British Association Report for 1858, he gives data compiled by Mr. David Milne[16] respecting the Lisbon earthquakes of 1755 and 1761, from which data the tables of velocities (p. 89) have been calculated, omitting those which Mr. Mallet has marked as uncertain. The distances are marked in degrees of seventy English miles each, and the time is reduced to Lisbon time.