308 Manurial Properties of Clay from Gas- Works. 



was taken up that the green extremities of the leaves tasted 

 strongly during all the period of growth. The only peculiarity 

 noticed was the tendency to rot from wet when blanching. In 

 another case soot was applied in excess to the surface of the 

 earth only, and not to the plants, and so much was taken up that, 

 after blanching, the celery was uneatable owing to the flavour of 

 soot. Corresponding with these facts, we have that of weeds grow- 

 ing upon the sites of old dunghills which have been known to con- 

 tain such an abundance of nitrates as to deflagrate when burnt. 

 Bearing in mind these instances, I watched the grass to see if any 

 corresponding effect was produced, and again the blue compound 

 was taken up, the blades being dyed and passing afterwards to the 

 same luxuriant green as marked the broccoli, while other plants 

 died of repletion and left a record of what had happened in their 

 blades, which were as blue as if dyed by indigo. Many similar 

 instances have been observed since, and, indeed, any one can 

 repeat them at will. The tendency of these facts seems to be 

 that the blue compound is taken up by, and circulates in, the 

 sap in an unaltered condition, and that within certain limits 

 it does no harm, but good ; and that when these limits are ex- 

 ceeded it injures or kills according to the quantity supplied and 

 taken up. Tliis power of destruction is not peculiar to the 

 substance as such, but is shared equally by guano, urine, sul- 

 phate of ammonia, and other concentrated fertilizers, and when 

 the plant appropriates such substances as nourishment and con- 

 verts them into the material of its own structure, it arranges 

 them in some new and suitable combinations. 



When this blue compound was taken up in an unaltered con- 

 dition 1 had serious doubts about the suitability of grass thus 

 grown for feeding purposes. These doubts were shaken when 

 Mr. Harrison said 'of Turner's grass that " the feeding quality 

 was as good as the quantity was large ;" though, as the manure 

 had then been applied to the field for six months, and the blue 

 compound could not be seen in the leaves, I regarded the testi- 

 mony as far from conclusive. All doubt, howevei-, is now re- 

 moved, for upon a part of one field dressed with the saturated clay 

 this year I saw the grass eaten as bare as if the land were shaved, 

 Avhile there was abundance of grass on other parts ; and Mr. 

 Bennett of Horncastle, who applied his manure in March last to 

 a single acre in each of two fields, writes me " that cattle are 

 much fonder of grazing on the portion of the field dressed thus 

 than on the other part." I shall not presume to question animal 

 instinct, but the result is the very opposite of what was to be 

 expected from the foetid compounds employed in the dressing. 



During the winter of 1855-6 the manure taken from the purifiers 

 of the Wakefield gas-works was thrown into the open yard, where 



