[20] 



[Appendix. 



II. Substance of a Memoir by M. Jean Thouin, on the Use of the 

 Scoria of the Forge in Horticulture ; printed in the Annates du 

 Museum, Vol. xvi. page 35. Translated by Mr. John Turner, 

 Assistant Secretary. 



Read April 6, 1819. 

 The injury which plants, in pots, sustain from the ravages of 

 worms and other insects, induced M. Jean Thouin to turn his 

 attention to the discovery of some mode of preventing it. Find- 

 ing the Scoria of the Forge a cheap material, on account of the 

 very limited demand for it in France, he resolved to make trial of 

 it, not only as a basis in the open air, on which pots were to 

 stand, but also in the houses where no bottom heat from tan was 

 required : this he adopted, after many fruitless experiments with 

 other materials, and his success was equal to his hopes. The way 

 in which plants in pots are most injured by worms and other in- 

 sects, M. Thouin conceives, is by their insinuating themselves 

 into the mould through the aperture at the bottom of the pots, 

 attracted by the freshness of the earth, through which they open 

 passages, and thereby not only admit the external air in too great 

 a quantity to the roots of the plant, but suffer the water which 

 may be given to it to flow off without benefiting the roots ; and 

 at the same time permitting the siliceous particles to escape, 

 leave nothing but a compact and inert mass, in which the roots 

 are compressed without nourishment. 



In forming his platform in the open air, M. Thouin proceeds 

 thus : in such situations as he intends to place his pots, he spreads 

 the Scoria very evenly over the surface of the ground, four or five 

 inches thick, having previously run it through a riddle, thereby 



