General Meeting.

C. Hulke, F.C.S., President, in the chair.

Papers.—1. “On Terrestrial Magnetism,” by the Hon. Robert Hart, M.L.C. (Transactions, p. 129.)

The Hon. R. Pharazyn said that on hearing the paper read he had been impressed by the fact that it contained several ingenious theories which would require a great deal of careful examination before they could be accepted as sound. Mr. Hart's statement that “the earth in its diurnal revolution cuts the lines of physical force which hold the earth in its place,” seemed a very metaphysical one. What are “the lines of physical force,” and how could cutting them produce friction? Then, again, what evidence had we that the increase of sun-spots increased the force of gravity?

The Hon. R. Hart explained that what he meant was that sun-spots were caused by the removal of the cloudy envelope of the sun's photosphere, which thus permitted the action of gravity to be more intense. It was like the removal of a blanket from before a source of heat.

The Hon. R. Pharazyn.—Precisely; but that is what I deny to be possible. Gravity is a force which acts according to what is commonly stated as the law of inverse squares and direct mass. Now, there is not the slightest reason to suppose that this force can be affected, as light and heat may be, by any screen placed between the attracting bodies. Were this the case it would be an easy subject for mathematical calculation, and, considering the immense amount of attention that has been directed to the theory of gravitation, I do not see how it could have escaped notice. Then, too, if what causes sun-spots “intensifies the action of the sun's gravity,” its effect would be apparent in astronomical observations and in the mathematical deductions based upon them. Nothing of the kind is ever heard of, however. I fancy Mr. Hart has confused certain magnetic forces with those of gravitation. Under certain conditions magnetic lines of force may be developed which, when cut by a moving body, offer what I think Professor Huxley has described as a sort of “sticky resistance,” like the resistance caused by an imperfect fluid. There is, however, nothing analogous to this in gravitation. There are several other points in Mr. Hart's paper which I might touch upon, but I will not take up the time of the meeting any further. On the whole I am inclined to think, “as at present advised,” that, ingenious and suggestive as Mr. Hart's paper is, a careful examination of it would show that the theories advanced in it are not in accordance with physical facts.

Sir J. Hector, although he must differ from the author, was pleased to hear a paper on this subject, especially as it brought up the question of magnetic observations. Nothing had been done in the matter since the first surveys. He believed the same instruments could be obtained again for use, so that the magnetic survey could be brought up to the present date. It would be a most important adjunct to the Geological Survey in detecting deep-seated lodes and faults, &c.

Mr. Tregear did not think dry air could produce sufficient friction to account for Mr. Hart's theory.

Mr. Travers said the magnitude of the sun must be taken into consideration in relation to its distance, and it was not surprising that it should exercise magnetic effects on our globe. There were many cases of intense electrical disturbances.

The President said it was difficult to give an opinion without studying the paper. Sun-spots did affect the earth as magnetical disturbances. There was a connection, but beyond that he was not prepared to go at present.