340 Mr. R. Adie on Ground Ice found in 



altered intercellular substance, acquired a still darker hue, whilst 

 those, on the contraiy, which were stained by the reduced silver 

 became somewhat paler, as if a portion of the argentine film were 

 soluble in that menstruum ; though it should be observed, that 

 no further effect was produced on the stain even by a protracted 

 digestion in ammonia. Now, upon making comparative experi- 

 ments with a piece of the linen wrapper that had been recently 

 ' marked ' in the usual way with a solution of nitrate of silver, 

 the fibres were found to present a very similar appearance to that 

 before described; the only difference being that the yellow 

 coloration was not quite so distinct, and more of the silver- 

 stain was removed by the solution of ammonia ; whereas on the 

 other hand, fibres that had been stained by solutions of chloride 

 and oxide of silver in ammonia were uniformly coloured of a dark 

 brown or black, and exhibited no trace of yellow coloration. 



These results, conjoined with the corroded state of the linen in 

 the vicinity of the marks, justify us, I think, in concluding that 

 the ancient Egyptians were really acquainted with nitric acid ; 

 and, as my father has already suggested, employed the nitrate of 

 silver as a marking-fluid. In what manner, however, they pre- 

 pared the acid, whether by the distillation of the nitrate of soda 

 or nitrate of potash with oil of vitriol, or by one of the processes 

 adopted by the alchemists, I will not at present attempt to decide, 

 but will leave the problem to be solved at some future period, 

 when the researches of antiquarians shall have offered us further 

 evidence on the subject. 



Mansion House, Old Park, Bristol, 

 March 27, 1853. 



LVI. On Ground Ice found in the Beds of Running Streams, 

 By Richard Adie, Esq., Liverpool"^. 



FOR the information of those who may not have turned their 

 attention to this subject, it may be desirable that I preface 

 my remarks by stating that ground ice is the name given to soft 

 snow, like accumulations of ice, found only in the beds of run- 

 ning streams. In the Thames the watei-men of the last century 

 were familiar with ground ice, and it was then made the subject 

 of accurate descriptions, but at that time no one attempted to 

 account for its appearance ; this has been rcsciTcd for a com- 

 paratively recent period, when Dr. Farquharson, M. Arago, and 

 Dr. John Davy have made the causes of the appearance of ice in 

 an unnatural position under water the object of their study. 

 The theories they have offered for explaining the formation of 

 ground ice are based on the supposition that the ice is formed 

 * Communicated by the Author. 



