116 Mr Robert Were Fox on certain 



pious precipitates when tested by muriate of barytes and ferrocya-* 

 nate of potash ; — shewing the presence of much sulphuric acid and 

 iron. Oxalate of ammonia, and nitrate of silver, indicated, more- 

 over, the presence of lime and muriatic acid. The saline matter in 

 this water (mostly sulphate of iron), was equal to one-tenth of its 

 weight ; and if it contained any common salt, of which I am not 

 clear, the proportion was very small indeed. Litmus paper showed 

 no excess of acid, the nature of which was not ascertained. 



Many of the pseudo-morphous crystals are more than an inch in 

 diameter, and are partly, or entirely filled with crystalline quarts, 

 whilst others are empty, or partly filled with more or less nume- 

 rous fragments of disintegrated fluor. I counted nearly a hundred 

 of such fragments taken from one of the crystals, or cavities, exclu- 

 sive of many other very small pieces. All the fragments are cor- 

 roded, and indicate, by their rounded edges and indented surfaces, 

 the action of a solvent which penetrated most readily between the 

 planes of cleavage.'^ Besides this disintegrated fluor, perfect octo- 

 hedrons of fluor occur in the same specimens ; but they were rather 

 more embedded in the quartz, and more protected from injury than 

 the others. Water was found alone in some of the pseudo-morphous 

 crystals, or cavities, and in others, it was found with fragments of 

 fluor, or with crystalline quartz. 



The most perfect octohedrons occur within large cavities in the 

 quartz. Some of the latter are more than two inches in diameter, 

 having the same form, and their sides generally parallel to those of 

 the former. 



The quartz specimens to which the crystals are attached, present, 

 when broken, the appearance of fortification agate, having lines pa- 

 rallel to their structure, of transparent and milk-white quartz, dif- 

 fering in thickness : these seem to indicate that the siliceous matter 

 had been deposited at intervals, of greater or less duration, or at 

 least, under different circumstances. After a time, an entire change 

 of conditions apparently occurred in the vein, and octohedral crystals 

 of fluor were formed on the quartz ; then silex was deposited either 

 in a compact form, or in minute crystals, and coated the crystals of 

 fluor ; afterwards, fluor again appeared, forming octohedrons over the 

 others, and mostly with sides and angles parallel to them. These 

 processes appear, from some of the crystals, to have been again re- 

 peated :- — then came a coat of silex over the fluor, or, judging from 

 the lines, many coats of it, forming a thick crust, having a surface 

 of small quartz crystals. Some specimens were found at the same 

 time with one or more layers of quartz, between two or more portions 

 of fluor, which tend to confirm these views. 



* When crystals of alum were kept for a time in water, the planes of 

 cleavage were first acted on, and fragments were separated from the 

 crystals resembling those of the disintegrated fluor. 



