﻿216 Mr. D. Vaughan on the Secular Effects 



greatly diminished ! the mass, being so very small in proportion, 

 will follow completely the impulse of the motion produced by the 

 electric current, and. be decomposed in quick succession into its 

 constituents, which are afterwards again united. Therefore tubes 

 filled with combinations of carbon and hydrogen show the lines 

 of carbon and those of hydrogen ; tubes filled with carbonic 

 oxide or carbonic acid gas show those of carbon and oxygen, 

 giving, in fact, a spectrum of carbon, because the extremely 

 small pressure and the high temperature cooperate in reducing 

 the carbon to a gaseous condition. Tubes filled with cyanogen 

 are not adapted for the observation, because the capillary tubes 

 become immediately blackened by decomposed carbon, by which 

 means observation is prevented. 



[Professor Lielegg's paper is accompanied by a Plate contain- 

 ing diagrams of the solar spectrum with the more important of 

 Fraunhofer's lines, the spectrum of olefiant gas and of coal-gas 

 (which are identical, except that the latter terminates at 82), 

 and the spectrum of the Bessemer-flame. These, however, are 

 not essential to the paper, and are here omitted. — W. T. L.] . 



XXIX. The Secular Effects of Tidal Action. 

 By Daniel Vaughan, Esq.* 



N tracing the mutual relations between the physical forces, it is 

 important to show that the occurrence of tides, while attended 

 with friction and with a consequent development of heat, must 

 involve some permanent alteration in the momentum of the vast 

 orbs which are concerned, either in exciting or in restraining the 

 great movement of the liquid domain. An estimate of the 

 amount of the minute changes which this cause may slowly oc- 

 casion in planetary motion is also intimately connected with 

 some of the great problems of practical astronomy. The earth 

 and the moon have been found to differ slightly in recording- 

 time since the earliest astronomical observations; and much of 

 this difference is now generally ascribed to a gradual reduction 

 in the diurnal velocity of our planet as its watery envelope is 

 alternately elevated and depressed by lunar attraction. The 

 vast tidal force which some of the satellites of Jupiter and Saturn 

 must feel, in consequence of the powerful attraction of the pri- 

 maries, would be sufficient to cause perpetual oscillations even 

 in the solid matter of these subordinate worlds, if they were not 

 secured by some special means against such desolating effects 

 from the great disturbance. But it is reasonable to suppose 

 that the motion of the satellite would change in proportion to 



* Communicated by the Author. 



