50 EEPORT — 1872. 



promulgated by Sir Johu Herscliel. The coiTections supplied by more recent arid 

 trustworthy observations have afforded a new set of data ; on the basis of which it 

 has been argued by the Author that such a Circulation tnust necessarily talis place 

 under the conditions above specified, and that it gives an adequate scientific ratio- 

 nak for the facts determined by observation. 



This view, however, though accepted by Sir John Herschel shortly before his 

 death, has been contested by Mr. James CroU; but his argument is directed, 

 not against the doctrine advocated by the Author, but against a doctrine set up by 

 himself. Instead of regarding the level of the Polar and Equatorial columns as the 

 same, and considering what will be the effect of their difference of gravity, he 

 estimates the difference of level which would be produced by the elevation of the 

 average temperature of a column of Polar water to the average temperature of a 

 column of Equatorial water of the same height, and then calcidates on this basis 

 the gradient which the surface of the sea would possess along the quadrant. This 

 gradient being far smaller than that which experiment has shown to be necessary 

 to produce a sensible fiow of water over a solid surface, it is assumed by Mr. CroU 

 that this difference of level wiU be constantly maintained, and that the weights of 

 the two columns will remain equal ; so that there -sviU be no such disturbance of 

 equilibrium by the constantly renewed action of Polar Cold; as the Author has 

 maintained. 



But it appears to him that Mr. CroU, (1) in assuming that such a difference of 

 level TviU constantly persist, disregards that fundamental principle of Physics which 

 teaches that fluids "will always tend to uniformity of level; and that (2) in relying 

 upon experiments which relate to the movement of Water over solid surfaces, he 

 commits the grave error of ignoring the fact that, as shown in the semidiurnal 

 passage of the Tide-wave, sensible movements of water upon loater are producible 

 by a force that bears a far smaller proportion to that of Gravity than that which is 

 assumed by him to be requisite. On the other hand, Mr. CroU does not attempt 

 to show how the almost Polar coldness of the Deep-Sea bottom, even under the 

 Equator, can be constantly maintained, except by a continual flow of Polar water 

 from the Polar to the Equatorial area ; nor does he show how it happens that a 

 disturbance of Thermal Equilibrium which must be constantly undergoing renewal 

 can be without its efiect in producing such a contmual movement of Ocean- Water 

 as takes place in all collections of fluid that are unequally heated. The primum 

 mobile of the Circulation advocated by the Author is Cold, which, when applied to 

 the sitrface, seems to him precisely the equivalent of Heat applied to the bottom, — 

 as in the ordinary apparatus for warming buildings by hot water. 



If Cold were continuous! j' applied to a portion of the surface of any collection 

 of Water, however large, and the liquid were not warmed again elsewhere, either 

 by conduction or radiation, the effect of such Cold would be to produce movements in 

 the liquid, by which the wJiole of it would be at last reduced to a low uniform tempe- 

 rature ; when all movement would cease. But if, while Cold is continuously applied 

 at one part, Heat is continuously applied at another, it is submitted that a Vertical 

 Circulation must be produced, which wiU be kept up as long as these antagonistic 

 conditions are maintained. 



The Author, not claiming more for himself than the abilitv to apply the Elemen- 

 tary^ principles of Physics uuder the guidance of Educated Common Sense, submits 

 the foregoing to the consideration of the distinguished Mathematicians and Physi- 

 cists of Section A ; who are much better judges than he can be of the soundness of 

 his views, and of the validity of the objections raised by Mr. CroU. 



Oil Recent Estimates of Solar Temperature. By James Dewae, F.R.S.E. 



After referring to the recent discussion on the temperature of the sun, in which 

 Secchi, ZoUner, Vicare, Deville, and Ericsson have taken part, the author proceeds 

 to group all the known methods of arriving at a knowledge of high temperatures 

 imder eight different processes. The following Table gives the names of the phy- 

 sicists who have specially employed each process, together with the principle on 

 which it is founded :— "^ 



