446 



Mr. W. Crookes. 



[Feb. 17, 



motion was 0*3 millim. Another earthquake (on November 10), 

 which, judged by its shaking effects on houses, &c, seemed to be of 

 much greater violence than the first, gave a record which showed 

 that its greater intensity was due, not to greater extent of movement, 

 but to greater frequency in the waves ; for their amplitude was even 

 somewhat smaller, but their frequency about three times greater than 

 in the former case. There were, however, at the beginning of this 

 earthquake a few waves of long period, upon which the above- 

 mentioned short waves were superposed : after them the motion con- 

 sisted of nothing but an irregular ripple of short waves. 



These results show that a higher ratio of multiplication is desirable. 

 The description which has been given applies, with insignificant modi- 

 fications, to the instrument now in use at the University of Tokio. In 

 making a second instrument the writer would introduce some changes 

 by way of adding to the stability of the bob and diminishing the 

 friction. Its mass and its moment of inertia might be increased with- 

 out increasing the distance between the axes bb and ee, by making 

 it in the form of a hollow ring, and placing the vertical part of 

 the lever c inside. To reduce the friction connexion between the 

 lever and its supports on the line ee might be given by pressure 

 against horizontal friction wheels, two at the top and two at the 

 bottom, the fifth degree of constraint being supplied by the pressure 

 of a rounded steel foot against an agate plate in the base. Other 

 modifications might be mentioned, but the author's object in this 

 paper has been not so much to describe constructive details as to ex- 

 plain the principle on which the action of the new seismograph 

 depends. 



February 17, 1881. 



THE PRESIDENT in the Chair. 



The Presents received were laid on the table and thanks ordered for 

 them. 



The following Papers were read : — 



I. " On the Viscosity of Gases at High Exhaustions." Bj 

 William Crookes, F.R.S. Received December 26, 1880. 



(Abstract.) 



By the viscosity or internal friction of a gas, is meant the resistance 

 it offers to the gliding of one portion over another. In a paper read. 



