to determining .the magnitude of material particles. 11 



was attained, since it served to point to a method of entry 

 upon a new and interesting field of inquiry. 



The phsenomena of exosmose which science has of late 

 years made known to us, especially through the valuable ex- 

 periments of Professor Graham, differ from that of the expe- 

 riment under consideration in being of an elective character ; 

 the transmission varying indeed with the density of gaseous 

 fluid, but yet taking place spontaneously, or in a manner that 

 scarcely admits of a mechanical explanation. Whereas in 

 the case under consideration the fluids were in a state of so 

 great compression within the vessels, that those which passed 

 through their pores were forced out chiefly in a mechanical 

 way. 



The material of the vessels was an aluminous composition 

 of considerable density made into bottles of a spheroidal shape, 

 and into these the substances experimented on were con- 

 densed. 



The means for the experiments offered themselves in a 

 manufactory of factitious mineral waters I was led to establish 

 in the East Indies, at the suggestion of friends, by which a 

 course of experimental pursuits, commenced from the time of 

 my entry into that country, were diverted from a philosophical 

 into a commercial channel. Works, however, were thereby 

 established, as in the case of many of our manufactures here, 

 yielding apparatus which might be employed in scientific ex- 

 periments, and which for the sake of philosophy alone never 

 would have been constructed. 



Earthy minerals may be compounded in a great variety of 

 mixtures, both as to proportion and to mechanical division, 

 which upon being exposed to heat shall undergo various kinds 

 of hardening and condensation ; and there are many which 

 pass into different degrees of vitrification, though few can be 

 turned to any useful purpose, for reasons curious in their 

 kind, but which it would be out of place to detail here. 



Of the few useful vitrifiable earthy combinations, some in 

 which silica predominates, with a lime or gypsum flux, un- 

 dergo little condensation up to a certain temperature, when 

 a partial fusion suddenly takes place, and a vitrified and 

 sometimes beautiful texture is obtained where the heat is 

 nicely under command. Of such compounds I had several 

 varieties, but they are not of a nature suited to the objects of 

 the experiment; and I refer to them only that in any repeti- 

 tions of it compositions of this nature might be avoided. 



Another class of vitrifiable mixtures may have a body 

 chiefly aluminous, and one of these combined with a felspatic 

 earth and a small proportion of iron oxide produced the ware 



