(8) That owing to the form and action of the ethereal corpuscule it will adjust itself to the surface with which it is in contact. More strictly, since the ether penetrates all bodies, the corpuscules will adjust themselves according to the nature as well as to the form of the surface.

If the ether is composed of rotating corpuscules then, by contact with the earth, their velocity of rotation will be gradually reduced, and according to the theory explained in the former paper these corpuscules will combine with the solid matter which they have penetrated. In this way the earth would grow larger by the addition of matter which has been reduced to an ordinary state, that is to matter as we commonly understand it. The matter of the ether may be described as matter in an “extraordinary state.” Astronomers maintain that the earth is growing larger, however gradually, and but very recently the view was put forward that this gradual increase in the size of the earth was due to showers of meteoric stones. The total quantity of meteoric matter, however, falling on the earth, was found by calculation much too small to produce the increase in the size of the earth. Professor Seeley, in a course of lectures on geology, delivered three or four months ago at the Royal Institution, expressed his conviction that the earth was being increased in size by some gradual process of addition.

The corpuscules of the ether are so constituted and act in such a manner as to adjust themselves to a flat surface, so that their outsides will revolve in the direction of that surface. More strictly it should be said that the ethereal corpuscules adjust themselves to what may be called a predominating surface. By a predominating surface would be understood a surface that has the greatest influence on the direction of rotation of the corpuscules. The solid and immovable land would have a greater influence than the mobile ocean, and dense solid matter than relatively lighter matter. The plumb-line has been found to be deflected from the true or astronomical vertical, in two ways, both probably owing to the same cause. The first is well known. Mountains deflect the plumb-line from the true vertical. In mountainous countries, as near the Alps and Caucasus, this deflection amounts to as much as 29″ of arc. The other case is this, the plumb-line hangs perpendicular to the surface of still water always, but the direction of the plumb-line is very frequently not in the direction of the centre of the earth. As bearing on this point, though not clearly understood, the following extraordinary facts should be quoted:—

“At sixteen astronomical stations in the English survey the disturbance of latitude due to the from of the ground has been computed, and the following will give an idea of the results:—At six stations the deflection is under 2″, at six others it is between 2″ and 4″, and at four others it exceeds 4″.

There is one very exceptional station on the north coast of Banffshire, near the village of Portsoy, at which the deflection amounts to 10″, so that if that village were placed on a map in a position to correspond with its astronomical latitude, it would be 1,000 feet out of position ! There is the sea to the north, and an undulating country to the south, which, however, to a spectator at the station does not suggest any great disturbance of gravity. A somewhat rough estimate of the local attraction from external causes gives a maximum limit of 5″, therefore we have 5″ unaccounted for, or rather which must arise from unequal density in the underlying strata in the surrounding country. In order to throw light on this remarkable phenomenon, the latitudes of a number of stations between Nairn on the west, Fraserburgh on the east, and the Grampians on the south were observed, and the local deflections determined. It is found that the deflections diminish in all directions, not very regularly certainly, and most slowly in a south-west direction, finally disappearing, and leaving the maximum at the original station at Portsoy.”^*.

Professor Maxwell believes the ether to be made up of rotating corpuscules fixed in space. That the ether is composed of rotating corpuscules is also the expressed opinion of Mr. Preston, who has made a special study of the ether. Sir William Thompson has shown that magnetic attraction is a rotational effect. Sir John Herschel expresses the opinion that the ether is composed of corpuscules, and says in a very decided manner that they must be fixed in space, and that they may rotate. The writer of this paper had expressed views in strict accordance with these just given. He has endeavoured and still endeavours to show that gravitation is a rotational effect, and, if so, that the ether, or “electric fluid,” is the physical agent producing gravitation. Now, as the ether penetrates all bodies and comes in contact with them the velocity of rotation of the corpuscules becomes gradually much reduced by this contact. Eventually these corpuscules combine with the bodies they penetrate, probably making them more dense and also adding to their mass and bulk. Solid rock would have a greater effect in reducing the velocity of rotation of the ethereal corpuscules than earthy or gravelly beds. Consequently all the striking solid features of the earth would become rather exaggerated than reduced by the direct action of the ether alone. “The Uniformitarian Theory” in geology declares that the basis upon which it stands is “that the continents have always been continents and the oceans oceans.” The great features of the earth “persist.” Whatever great features now exist—as the Himalayas and the Alps, the deep basins of the Atlantic and the Pacific—have always existed in their characteristic features.

The rotation of the ethereal corpuscules within the surface of the earth would be so considerably reduced that the force of gravity would be lessened. The corpuscules, whose rotation had been reduced, would react on those at and probably immediately above the surface of the earth. According therefore to the nature of the layer of the earth's crust, whether of greater or less density, so would vary the force of gravity very near the earth's surface. Where these layers were very dense there the force of gravity would be less. In a very hard rocky country the force of gravity would therefore be less than at the surface of the ocean. If a mountain is more dense than the surrounding country the force of gravity on the top of the mountain should be less than on the surronnding plains. Until the nature of an accelerating force is understood, the principles here sketched cannot be extended with any satisfaction beyond the surface of the earth.

The following bears directly upon what has just been said:—

“An immense number of pendulum observations are now being made at the astronomical stations of geodesical surveys in Germany, Russia, and India, which, when fully published, will throw light more perhaps on the local variations of gravity than on the figure of earth. The observations made at the various stations of the Indian meridian arc bringing to light a physical fact of the very highest importance and interest, namely, that the density of the strata of the earth's crust under and in the vicinity of the Himalayan Mountains is less than that under the plains to the south, the deficiency increasing as the stations of observation approach the Himalayas, and being a maximum when they are situated on the range itself. This accounts for the non-appearance of the large deflections which the Himalayas, according to Archdeacon Pratt's calculations, ought to produce. The Indian pendulum observations also throw some light on the relative variations of gravity at continental, coast, and island stations, showing that, without a single exception, gravity at the coast stations is greater than at the corresponding continental stations, and greater at island stations than at coast stations.” The inference, that because the force of gravity in any locality is less, the density of the earth at that place is less, is one usually made, but it is more credible that mountains are denser than the plains which are made up of detritus from those mountains than that the plains are denser than the mountains.”^*

Prof. Darwin made experiments during last year, in which he discovered variations in the force of gravity. He has embodied the results of his investigation in a paper which was published in the November number of “Nature” last year. His investigations showed that the force of gravity varied at the very same place, that there was on one or two days a diurnal variation in the force of gravity.