197 



One useful hint which the chemist may derive from these observa- 

 tions is, that if he wishes to preserve alloxan, it ought to be got in 

 the anhydrous form, which is done by evaporating its solution at 

 140^^ or 150°, when anhydrous crystals alone are deposited in the 

 warm solution, which is poured off and further evaporated, as long as 

 it yields crystals. It is apt to be decomposed at higher temperatures. 



3. Observations on the Structural Character of Rocks. 

 Part IL By Dr Fleming. 



In proceeding to consider still farther the physiology of rocks, the 

 author proposed in this communication to confine himself to the 

 illustration of 



1. The Columnar Structure. — After enumerating examples of this 

 structure, as occurring in the neighbourhood of Edinburgh, in cannel 

 coal, sandstone, clay, ironstone, clinkstone, claystone, greenstone, 

 and basalt, he exhibited examples of similar appearances in oven soles 

 and fragments of the walls of vitrified forts. The ordinary explana- 

 tion of this structure as the result of cooling from a state of fusion 

 he pointed out as unsatisfactory, even in the case of basaltic pillars, 

 and inapplicable to similar appearances as occurring in sedimentary 

 rocks. He considered the whole phenomena explicable as connected 

 with one cause, viz., shrinkage, arising from the escape of aqueous 

 or volatile matter. 



2. The Cone in Cone Structure. — Examples of this structure occur 

 in impure ferruginous limestone at Joppa, the Water of Leith, and 

 other places, in connection with the coal measures. The author re- 

 ferred the origin of this structure to shrinkage, conjoined with a cer- 

 tain amount of molecular aggregation, or crystallising influence. 



4. Some Observations on Fish, in relation to Diet. 

 By Dr John Davy. 



In this communication the attention of the author is chiefly di- 

 rected to two subjects of inquiry : — 



Ist^ The comparative nutritive power of fish, taking the specific 

 gravity of their substance, and the proportion of solid matter left on 

 thorough drying, as a measure of the same. In illustration, two 

 tables are given, containing the results of trials on several kinds of 

 fish and other articles of animal food : from which he deduces that 



