Page:Proceedings of the Royal Society of London Vol 1.djvu/155

Rh portion of sulphur obtained from it by analysis being exactly the total quantity that should be contained in the three sulphurets of which this substance consists. The speciﬁc gravity of this substance, compared with those of its ingredients, also indicates that the com- bination is attended with an expansion nearly proportionate to the numbers 6000:5765.

2. The author, proposing to avail himself of the opportunity af- forded him by this inquiry, to enter into an investigation concerning the various ores that are produced by the combination of sulphur and copper, of the nature of which neither mineralogy nor chemistry has yet supplied us with any certain information, thinks it necessary, in the second part of his paper, to offer some remarks concerning the different modes of attraction that appear to inﬂuence the formation of mineral substances.

Two kinds of attraction have hitherto been admitted to prevail in the formation of mineral substances, viz. the attraction of composition, and the attraction of aggregation. The former, which is more generally known by the name of chemical attraction, takes place only between the most simple or primitive molecules of a substance; which, however, must be of dissimilar nature : and to its action is owing the formation of new, or, as they may properly be called, secondary or integrant molecules; because they, and they only, determine the nature of all the compound bodies belonging to the mineral kingdom. The difference existing between mineral bodies is now said to depend—1st, Upon the nature of the primitive molecules, by the combination of which they are produced; and 2ndly, Upon the proportion in which these molecules, supposing them to be the same, are combined together. The combination of these secondary molecules is effected by the attraction of aggregation, which unites them into one or several masses. perfectly homogeneous in all their parts. This attraction of aggregation seems to he susceptible of various modiﬁcations, which alter its manner of acting upon the constituent molecules. Of these, two are here mentioned:—1. The crystalline attraction of aggregation; and 2. The simple attraction of aggregation. The former always takes place between similar molecules, and is either regular, irregular, or amorphous. The ﬁrst of these produces solid bodies, which are either constantly of the same form, or subject to certain laws of variation, which are always capable of being referred to the same primitive form. This, like all other crystalline attractions, can only take place in ﬂuids, which, among other conditions, must be at rest when it is operating. When the ﬂuid happens to be agitated, the crystallization will then he of the second kind, and the forms produced will be irregular : and when the agitation of the ﬂuid is still greater, small irregular detached masses will subside, and unite together by a mode of attraction, which is here called simple homogeneous attraction of aggregation, of which instances are given in the granulated quartz and granulated carbonate of lime. This attraction operates at times simultaneously with the simple homogeneous attraction; and then the granulated masses, instead of