3 20 Miner a hgy. 



themfelves from impure juices by the means of excretions *i 

 He placed that plant in a tranfparent velTel filled with watery 

 and obferved every dav, at the extremity of the roots, a 

 fmall drop of a vilcous matter. This drop he removed, and 

 next day there was another. All plants emit, in the fame 

 manner, from the extremities of their roofs, and particularly 

 during the night, fmall drops of a liquid which is extremely 

 prejudicial to them. It is hurtful alfo, very often, to thofe 

 plants which are near them ; at other times it is ufeful to 

 them : thus oats fuffer much from the ferratula arvenjis ; 

 flax, from the euphorbia pcplus and the fcabious of the 

 fields; wheat, from the crigeron acre', farrafin, from the 

 fpergula arveti/ls ; and carrots, from comfrey. 



Thefe phenomena may ferve to explain why farmers are 

 obliged to let their lands reft a year ; for, during that interval, 

 this humour has time to be decompofed. By the fame 

 means may be explained, why land exhaufted with one kind 

 of plant caufes others to vegetate with vigour : the faeces of 

 the former hurt plants of the fame fpecies, and ferve as 

 manure to others. A field, for example, exhaufted with 

 bearing clover, if fown with wheat, will produce an abun- 

 dant crop, becaufe the faeces of the clover are^ without doubf, 

 a manure for the wheat. 



MINERALOGY. 



A very lingular fpecies of iron ore has lately been difco- 

 vered in Shroplhirc, which may truly be confidered as a na- 

 tional acquifition. It yields, on the firft reduction, malleable 

 iron, inftead of caft iron, as is ufual from other ore3 ; and 

 the product is very large. From an hundred parts of it, 

 previouflv torrefied, which we reduced in the allay furnace 

 in the common manner, we obtained a malleable button 

 which weighed fixty-feven parts. The ftratum, which is of 



* Phviias animalium more cacare primus exphravh vir indefrjfus Brag' 

 mania, fuys Humboldt in bis Apfcoritms Flora Fribergefifii. 



the 



