308 Sin James Hall on the Consolidation of the Strata. [Oct. 



Gibraltar. We have reason, then, to conclude, both that the 

 surface of the Mediterranean is Jower than that of the ocean, 

 and likewise that the quantity of salt in the former is perpe- 

 tually on the increase ; so that the specific gravity of the waters, 

 jand the intensity of their saturation, must be perpetually ad- 

 vancing to a state of brine. I am well aware, that an attempt 

 has been made to render such a conclusion unnecessary, by the 

 supposition of a counter-current flowing at the bottom, out of 

 this great basin; but such suppositions are, in my opinion, alto- 

 gether gratuitous. 



AVhat is here said of the Mediterranean, will apply no less to 

 other seas, and even to the great oceans. And wherever a basin 

 occurs, in which a bottom of great depth is surrounded by a 

 ridge comparatively shallow, we may expect to find the lower 

 portion, at least, of the water in a state approaching to brine. 



Without any such theoretical explanation of the manner in 

 "which a supply of salt is supposed to be formed, it may perhaps 

 be considered sufficient for my purpose, to recal to the recollec- 

 tion of the Society, that there are in almost every part of the 

 world vast districts of rock-salt, and in some countries extensive 

 salt lakes and salt rivers; and in our own country we have 

 many instances of brine springs, besides rock-salt in abundance. 



Here then it seems to me, we are plentifully furnished with 

 the means of accounting, in the manner experimentally shown, 

 for the agglutinations of such gravel as that of Aikengaw and 

 for the strata of the Salt-Heugh, which, by an easy analogy, may 

 be transferred to sandstone in general, and, perhaps, to stratified 

 rocks of every description. 



A member of this Society, however, well known by his scien- 

 tific acuteness, alleged, first in his public lectures, and after- 

 wards, upon my requesting an explanation of his objection, 

 -again repeated, that I was not justified in such theoretical 

 conclusions, respecting the influence of heat at the bottom of 

 the sea, since the neighbourhood of the cool water would neces- 

 sarily counteract that influence. 



In answer to this difficulty, I must beg leave to remark, that, 

 in all my experiments above alluded lo, the sand (viewed by 

 means of the gun-barrel) was seen to become red-hot during the 

 process of consolidation, while the superincumbent brine 

 remained boiling above ; and it was even found easy, by supply- 

 ing cool brine in sufficient quantity, to maintain the temperature 

 of the fluid permanently such, that the hand could be plunged 

 into it at top, without injury, the sandstone below remaining all 

 the while at a full red heat. But whenever I repeated this, expe- 

 riment, with every circumstance the same, both as to duration 

 and temperature, as in the example above detailed, but in which, 

 instead of hx'me, fresh water was used, the result was very 

 different. The lower part of the gun- barrel, immersed in the 



