90 A PRACTICAL TREATISE 



plants are very groat, yet we are but imperfectly acquainted 

 with the extent or the exact manner in which its influence is 

 broug-ht into action, and ' we are in a great measure ignorant 

 of the actual changes that are produced upon the earth after 

 this manure has been applied.' It would, however, seem, that 

 where it exhausts, it is only by hastening the putrefaction of 

 the animal and vegetable matter in the soil, and by that 

 means applying a larger portion of those substances in a given 

 time than could be otherwise afforded to the growth of plants. 

 It is thus known to produce more luxuriant crops, and it will 

 also consequently enable the farmer to continue his land in 

 tillage, during a certain time, with more effect than if no 

 calcareous manure had been laid on; but, although it may not 

 tend to the deterioration of the original staple of the soil, it 

 can hardly be doubted that it nmst be thus more promptly 

 deprived of its fertility than if the exhaustion of that vegetable 

 mould with wliich it had been supplied by nutritive manure 

 were occasioned by a more gradual process of decomposition. 



That this is the only way in which effete lime can exhaust 

 land, seems probable from the large quantities of neutralized 

 calcareous earth which are often applied without any bad 

 effect in the form of chalk, shells, limestone-gravel, and the 

 whole tribe of marls. A larger quantity of these is often er 

 laid on in one year than would be used of lime in half a 

 century, were the land in tillage to be managed according to 

 the custom of some countries; yet it is not generally impove- 

 rished, and, in many cases, it is permanently improved. This, 

 however, is probably occasioned by its combination with other 

 substances, which either counteract its exhausting powers or 

 supply the waste of nutritive matter. It must, however, be 

 admitted, that this is not apparent in regard to chalk, which 

 is commonly applied in large quantities without any bad 

 effects ; and there are many instances of soils more naturally 

 fertile than perhaps any others that are known, and which 

 seem to consist almost wholly of calcareous earth; but were 

 their properties critically analyzed, itjij^still possible that they 

 might be found essentially different fi^i those which they are 

 commonly supposed to possess. 



A very eminent writer on agriculture, when treating of 

 stimulant manures, which are generally supposed to be only 

 of use when applied to rich soils, and when applied to poor 

 land would produce hardly any, or even hurtful effects, says, 

 in contradiction to that theory, — that 'he is firmly convinced, 



