Farming of Surrey. 



407 



bv the extent to which the marl-pits have been worked ; but we 

 are indebted to modern science for an accurate investigation into 

 the nature and composition of the substances referred to, and for 

 the consequent improvements in the method of manufacturing 

 and applying them to the land. * 



The principal deposits of fossiliferous substances are found at 

 the junction of the chalk with the upper greensand which lies 

 immediately below ; and also below the gait, and between it and 

 the lower greensand : they are also discovered in the gait itself, 

 but not in sufficient quantities to be made available. The writer 

 is not aware that any extensive discoveries of similar phosphoric 

 substances have been made in any other part of the county, there 

 is no doubt, however, that they are to be found more or less 

 throughout the entire length of the north downs, in the position 

 already indicated ; and where they occur in quantities sufficient 

 they must eventually become of considerable importance as a 

 native manure. The deposits in connection with the greensand 

 are frequently several feet in thickness ; and when this is the 

 case they become valuable for the purpose which is about to be 

 described, viz., as a cheap substitute for bones in the manufacture 

 of superphosphate of lime. 



According to the statement of Professor Way, in the 12th 

 volume of the Journal, in an article " On Superphosphate of 

 Lime : its Composition, and the Manner of Making and Using 

 it," we find that " The fossils of the upper greensand contain 

 from 55 to 60 per cent, of phosphate, and 8 to 10 of carbonate 

 of lime ; and those of the lower green sand from 38 to 40 per 

 cent, of phosphate, with little or no carbonate." As the whole 

 process of digging and grinding has been described in the article 

 by Messrs. Paine and Way, it will be sufficient to notice here, 

 that as the fossils are dug they are sifted in the same manner as 

 common gravel (the siftings are carted on the land, and in some 

 instances pay the whole labour of digging), they are then reduced 

 to powder in the mill which is " attached to the machinery of a 

 small threshing-machine ; it consists of two pairs of cylinders, 

 the upper one being fluted transversely. Scrapers, like those 

 used in a common bone-mill, are indispensable. Two horses 

 will grind from 2 to 5 tons a-day, according to the hardness of 

 the substance." To manufacture superphospha,te, of which laro-e 

 quantities are made on the farm of j\Ir. Paine, to every cwt. of 

 powdered phosphate of 1 ime are a dded 30 lbs. of sulphuric acid, 

 and 12 lbs. (3 quarts) of water ; the mixture is then thrown into 



* Foi' a detailed account of these most interesting investigations the reader is 

 referred to an article in the ninth volume of this Journal, ' On tlie Phosphoric 

 Strata of the Chalk Formation,' by Messrs. Paine and "Way, and to a more recent 

 article in the first part of this volume. 



