Professor Kelland's Note on Fluid Motion. 29 



I went from hence by Petherwin to the manganese mine 

 at " Bolathan," and there I observed the pale green killas had 

 been sunk through by a vertical shaft to a depth of twenty- 

 five feet (as I was informed) down to the Coddon Hill grit 

 and its lode of manganese. The killas here is unequivocally 

 exposed on the surface, and is an uninterrupted continuation 

 of that which near Petherwin abounds in Clymeniae, Gonia- 

 tites, Orthoceratites, Trilobites, Orthides, &c. &c. ; and if the 

 subordinate grit had been carted to the spot from Coddon 

 Hill in North Devon, or from St. Stephen's Down near Laun- 

 ceston, it could not have offered closer points of comparison 

 and agreement. 



The lower killas, the lowest of the threefold division into 

 which that great member of the Devonian group naturally 

 resolves itself, overlies the floriferous or carbpnaceous series : 

 not a shadow of doubt or uncertainty is on my* mind when 

 I state it ; the fact is proved by every variety and kind of re- 

 cognized evidence by which the established order of super- 

 position of rock formations has been determined elsewhere; 

 and those several kinds of evidence cannot be disputed or re- 

 jected here without insecurity and peril to the foundations of 

 the geological column, every stone of which has been hewed 

 and squared and adjusted by some wise master builder. If in 

 a perfect faith in, and uncompromising obedience to those 

 laws which alone govern legitimate and secure induction, I 

 have without pretension or design conveyed embarrassment or 

 perplexity to the minds of some, or unkind or unworthy feel- 

 ings to the minds of others, I am amply recompensed in the 

 conscious indifference and singleness of purpose with which 

 I have read off the great truths of the Creator, and in a dawn 

 of hope that, ere long, He may enable me to sound a dia- 

 pason note which may restore to harmony the apparently dis- 

 cordant elements. 



I have the honour to remain, &c. 

 Bleadon, May 17, 1842. D. Williams. 



V. Note on Fluid Motion. By the Rev. P. Kelland, M.A., 

 F.R.SS. L. $ E., F.C.P.S., %c 9 ProfeSsor of Mathematics 

 in the University of Edinburgh, late Fellow and Tutor of 

 Queen's College, Cambridge*. 



T^HROUGH the able and. interesting papers which Prof. 



-*■ Challis has recently published in the Philosophical 



Magazine fj attention has been directed to the circumstances 



* Communicated by the Author. 



t S. 3, vol. xix. p. 229. vol. xx. p. 84, 281. 



