Proceedings of the British Association. 439 



specific gravity is about 2'59. According to analysis, its principal con- 

 stituents are — 



Carbonic Acid, .. .. 4435 



Lime, .. .... •> .. »• •• •• 53-53 



Red Oxide Iron, 0-69 



Insoluble Matter, 1*26 



Loss, 0-17 



100-00 

 From the large proportion of carbonate of lime contained in this 

 limestone, it appears to be well calculated for agricultural purposes, 

 and is used to a considerable extent. 



The Chalk formation occupies a considerable extent in the eastern 

 part of the county, forming that peculiar feature in it known as the 

 Wolds. This substance scarcely requires any description. It is, as is 

 well known, of a white colour, and easily scraped with a knife, and 

 readily soils the fingers. Its specific gravity is about 2-55. According 

 to analysis, its chief ingredients are — 



Carbonic Acid, 43-00 



Lime, : .. 55-42 



Insoluble Matter MO 



Loss, # .. 0-48 



100-00 



This, like the preceding variety, appears to contain a large propor- 

 tion of carbonate of lime, and consequently affords, by burning, a simi- 

 larly large proportion of lime, and hence is particularly adapted for 

 agricultural purposes, although it is said not to produce so strong a 

 lime as the oolitic limestone. 



Sir J. Johnstone remarked on the very injurious effects produced, 

 in many districts, on the crops, by the use of the magnesian limestone, 

 and wished to know if chemists could at all account for the very re- 

 markable differences, which agriculturists found to exist in limestones, 

 which gave nearly the same products by analysis. — Prof. Daubeny ob- 

 served, that it was probable that the difference might be found in the 

 fact, that one limestone contained a larger portion of the phosphates 

 than another, In ordinary analysis, the phosphate of lime, being so- 

 luble in muriatic acid, was very generally overlooked. — Dr. Playfair 

 stated, that the existence of iron, in the state of protoxide in one stone, 

 and of peroxide in another, would explain the difference in the observed 

 effects of different limestones. He adduced some instances in which 

 clays, from the same pit, being used as manures, were found to possess 



3 L 



