Mr. R. Thomas's Reply to Prof. Whewell. 1 83 



and which, amongst other considerations, led the Navy Board 

 to try my plan for defending ships from lightning in the navy, 

 I have, for the reasons already assigned, thought proper to 

 offer ; they at the same time show the scrupulous care which 

 the Board exhibited on the occasion, and how much they 

 were alive to the question. 



[To be continued.] 



XXXIV. RemarTis on Prof Whewell's Paper on the Mean 



Level of the Sea. By Richard Thomas, Civil Engineer* . 

 f OBSERVE that Mr. Whewell has in the Philosophical 

 Magazine for November honoured with his notice my ob- 

 servations relative to the mean level of the sea, which were 

 inserted in the Magazine for August. I should not have 

 thought it needful to say another word about it, but leave the 

 matter to be determined, as I think it ought to be, by extending 

 the levels westward to the Land's-end, connecting these levels 

 with others which might be taken at convenient places across 

 from the north-west coast to the south-east of Cornwall ; but 

 it appears that Mr. Whewell has mistaken the drift of my 

 argument, by which I endeavoured to show, that owing to 

 the tides, the sea at Axmouth might be kept up to a higher 

 mean level than on the coast of Cornwall. I do not draw such 

 inference from the mere narrowing of the English Channel 

 by the projection of Cape la Hogue, but by that projection in 

 combination with the deeply embayed form of the opposite 

 coast of England between the Start and the Bill of Portland, 

 giving such directions to the tide-currents as would continually, 

 both on the flood and ebb, tend to set them over against that 

 part of the coast on which Axmouth is situated, and conse- 

 quently tend to keep up the level of the water there ; for it 

 must be kept in mind that at the time of high water at Ax- 

 mouth, the tide is strong flood in the Channel, and at low 

 water the ebb tide is strong; and there appears to be strong 

 evidence that the flood sets in the way I state, from the velo- 

 city with which it passes along by the back of Portland Island 

 and occasions the " Race " off" the Bill. 



Mr. Whewell says, " If the surface of low water were a 

 level surface, as Mr. Thomas supposes," &c. ; and in reference 

 to a comparison of the tides of Plymouth and Axmouth, that 

 " Mr. Tliomas has no authority either IVom theory or observa- 

 tion for assuming the higii waters to coincide," &c. &c. The 

 best answer I can give to these remarks, is a reference to my 

 paper as printed in your Magazine. 



However, as Mr. Whewell agrees with me in the propriety 

 * Communicated by the Author. 



