135 



portion of sulphur obtained from it by analysis being exactly the 

 total quantity that should be contained in the tliree 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 gene- 

 rally 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, se- 

 condary or integrant molecules ; because they, and they only, deter- 

 mine 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 mole- 

 cules 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 be 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 aggrega- 

 tion. 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 re- 

 ferred to the same primitive form. This, like all other crystalline 

 attractions, can only take place in fluids, which, among other con- 

 ditions, must be at rest when it is operating. When the fluid hap- 

 pens to be agitated, the crystallization will then be of the second 

 kind, and the forms produced will be irregular : and when the agita- 

 tion 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 



