399 



common salt, and some other mineral salts, are necessary 

 ingredients in the food of animals; and, amongst plants, 

 the class of Fungi, anomalous in so many respects, are so 

 likewise in this, that they feed upon organic principles 

 contained in decaying organized substances. 



Some few other points of comparison, or contrast, between 

 the animal and vegetable kingdoms, might be gathered, but 

 these seem to be the chief ; and a review of the whole serves 

 only to establish the original statement, that no exact limita- 

 tions can be laid down as the boundaries of these kingdoms ; 

 that the characters of one are imitated by beings belonging 

 to the other. Species alone seem to be exactly defined 

 in nature. All groups, including several species arranged 

 together for systematic purposes, insensibly glide into each 

 other; in the words of Linnaeus, Natura non facit saltus" 



The Chairman then called upon Mr. Thorp to read 

 his Paper : 



ON THE VENTILATION OF COAL MINES. BY THE REV. 

 WILLIAM THORP, OF WOMERSLEY, NEAR PONTEFRACT. 



I shall make no apology for the introduction of this subject 

 before the Geological and Polytechnic Society, as it is certain 

 that the person who would discover any safer modes of ven- 

 tilation, or even any additional precautions to those now in 

 use, and should succeed in having them generally adopted, 

 would be for ever conferring a lasting benefit upon the mass 

 of our mining population. 



Nothing can be more simple than the principle upon which 

 coal mines are ventilated. Atmospheric air descending by 

 one shaft, called the downcast shaft, is made to circulate 

 through the subterranean workings, and to ascend at another 

 shaft, called the upcast shaft. The ascending current of air 



