Page:The Geologist, volume 5.djvu/169

Rh by lava in its consolidation is fully discussed. In a lava when cooling there are centres of attraction more or less affecting all the crystalline particles; and in a uniform mass cooling throughout alike, these centres would be equidistant and the contractile force equal. "In this case all the spheres of attraction would be equally similar in size and form, and would arrange themselves as closely as possible, that is, in the manner of the cells in a honeycomb, or as the circles in the figure below.

"The fissures of retreat produced by the contractile force of all the spheres, acting contemporaneously, must evidently therefore divide the consolidated layer into hexagons, each straight fissure being tangential to the opposite spheres of attraction between which it is formed."

,—In a recent number of 'The Geologist' (February, 1862) appeared the description and a sketch of a Tertiary limestone on the River Murray, in Australia. In this limestone are a series of holes or warrens, inhabited by hosts of wallabies, kangaroo-rats, etc., and from these cavities there exudes a peculiar dark brown, sticky, odoriferous matter, in considerable quantities. This substance has been handed to me by Mr. Rupert Jones, F.G.S., for chemical examination. The result of my analysis is as follows:—