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The Need for Lime and How to Meet it. [June. 



with the constituents of the soil and dissolve; hence it is 

 important to know how small the particles of stone must be 

 in order that their function may be fulfilled. If the stone were 

 all reduced to impalpable dust, the o])ject would be attained; 

 this is, however, far from being a practicable proposition, on 

 the ground of both initial and running costs. We have, there- 

 fore, to decide, not what is absolutely the best, but what is 

 fine enough to give thoroughly satisfactory results in practice. 

 Not all authorities are agreed on the point of fineness in 

 grinding, but there is a very general belief that a fair mean 

 is struck between the ideal and the commercially practicable, 

 when nearly all the ground stone will pass through a screen 

 having ten meshes to the linear inch, and all the fine material 

 produced in grinding is included. This product contains about 

 10 to 15 per cent, of stone which is in too coarse a state of 

 sub-division to be immediately useful, but the reason it is 

 recommended is that the type of mill which will produce it 

 is much cheaper, and the power required to drive the mill is 

 so much less than for a similar output of finely ground stone, 

 that there is no doubt about the advantages attaching to the 

 rougher method. 



Experiments have been conducted both in this country and 

 in America in order to ascertain what is the actual size of grain 

 below which no appreciable improvement in fertilising value 

 can be detected. Although opinions differ it seems that particles 

 which pass through a 60x60 screen are at any rate fine enough 

 for all practical purposes. It might at first seem that ground 

 stone passing through a 10x10 screen would not be fine enough 

 to be of very much service; such a material, however, would 

 be found in general to contain about 70 per cent, small enough 

 to pass through the 60 x 60 screen. This is a fact not 

 infrequently overlooked by producers of very finely ground 

 but very highly priced agricultural limestone. In the matter 

 of distribution there is an actual advantage attaching to the 

 more coarsely ground product, for it does not tend to clog and 

 hang together like the very fine limestone dust, and for that 

 reason gives much less trouble in the distributor. 



The plant necessary to produce this comparatively r^oarsely 

 ground limestone is so compact and simple that it is possible 

 to mount it in portable form so that it can be drawn by a 

 tractor to any point where it can be fed conveniently with 

 broken stone. A tractor or other portable source of power 

 can be used to drive it. There are many makes of machine, 

 but the Disintegrator is the only type of mill which can be used 



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