Mr Prijdc on the Motion of the Sea. 77 



cially I intend to turn my attention to the investigation of 

 the liabihty of different kinds of oil to ignite spontaneously, 

 and also to the behaviour of the same oil under different 

 circumstances. Insurance companies, T believe, at present 

 make a different charge for insuring premises in which one 

 kind of oil is used from that which they make in the case 

 of certain others, this difference in rate being regulated, I 

 understand, by the supposed greater facility with which cer- 

 tain kinds of oil will ignite spontaneously. Whether these 

 peculiar rates are merely arbitrary, or are founded on some 

 proper basis, I am not aware ; but it appears to me — if my 

 information as to their charges is correct — that they are at 

 present rating exactly in an opposite way from what they 

 should do. Until my investigations are further advanced, I 

 cannot, however, speak with confidence on this subject. 



II. — 071 the Motion of the Sea, arising from the rotation of the 

 Earth on its axis, and the difference of tlie force of gravity, 

 on particles of eqiial rrtagnitude, at the surface and at the 

 bottom of the Sea. By James Pryde, Esq., Lecturer on 

 Mathematics in the Watt Institution and School of Arts. 



Mr Pryde stated, that on reading the various theories which 

 endeavour to account for these motions, he had been led to 

 ask the following questions : Is there any reason to suppose 

 that the under-currents of water which are known to flow at 

 the bottom of the sea towards the equator, and the surface 

 currents such as the Gulf Stream, which flow from the equator 

 to the poles, have anything to do with the rotation of the 

 earth on its axis, combined with the difference of the force of 

 gravity at the surface and bottom of the sea, caused by the 

 mass of the earth being much gTcater than a globe of water of 

 equal bulk, and the additional density of water at great depths 

 caused by its compressibility ? 



After performing many calculations founded on known 

 physical laws, tabulating the results, and applying these to 

 the subject of inquiry, he became satisfied that these motions 

 of the sea are as necessary consequences of the physical con- 

 .'titution of the earth as the tides or any other physical phe- 



