bottom of the bucket, we have no complete answer. All we can say is that the push is due to the fact that the water is heavy. This means that the water in our bucket is attracted towards the earth, but what kind of intervening link there is which transmits a force from the earth to every particle of water and every particle of bucket and rope we are quite unable to say. Everyday experience has so familiarised us with the action of gravity that we have become accustomed to simply accepting it as a fact in nature, without further inquiry as to the machinery which is instrumental in the transmission of this force through the intervening space. We simply say that gravity is a force that acts at a distance, and since by direct experiment and astronomical observation it has been found possible to formulate a mathematical expression for this force, there is, from a purely practical point of view, no need to find an explanation of the machinery by which this force is transmitted through space, whether the space be quite empty or filled with other bodies.
The confession of ignorance as to the nature of this machinery of transmission is, however, not a denial that such machinery exists; on the contrary, the conception that
