578 
Soil and Subsoil of' a Productive Field. 
2. — Subsoil. 
In 100 parts as actually found. 
Organic matters free from ammonia 1 • 20 
Hydrate water . . . 2-60* 
Carbonic acid . . • 0*0i 
Silicia .... 82*55 
Peroxide of iron . . . 3*70 
Lime .... 0-69 
Magnesia , . • . 1'5.> 
Alumina . . . . 4*48 
Potash .... 0-60 
Soda . . . .1-10 
Chlorine . . . .1-26 
Sulphuric acid . . . O-IC 
Phosphoric acid . . .a trace 
Loss on analysis . . 0*07 
100-00 
In 100 parts as contained in the soil. 
Organic matter free from ammonia 1 "20 
Hydrate water . . .2-60 
Silica and silicic acid . . 81-9fi 
Peroxide of iron . . . 3-70 
Carbonate of lime . . . 0-09 
Lime (probably as silicate) . 0'58 
Magnesia (probably as silicate) 1 '55 
Alumina () rincipally as silicate) 4 '48 
Sulphate of lime . . . 0*27 
Cldnride of sodium , . 2 '08 
Silicate of potash . . . 1'19 
Phosphoric acid . . mere trace 
Loss on analysis . . . 0'30 
100-00 
* Water not expelled by long-continued exposure to a water bath. 
The subsoil may be viewed as representing the soil in its natural condi- 
tion, and, as such, is rich in every constituent essential to fertility, with 
the exception of phosphoric acid, of which substance scarcely a trace 
could be detected. All the iron in the subsoil exists in the state of 
peroxide, so that the plants may appropriate its constituents without 
injury. The presence of so much common salt in the subsoil is only 
explicable on the supposition that it has been washed by the rains from 
the upper to the lower soil, for we find it absent except as a trace from 
the surface soil. Tlie vicinity of the soil to the sea explains the origin of 
the salt. 
The upper soil has obviously been improved by manure containing 
phosphates, and perhaps also of silicates. I regret that no information 
on this point accompanied tlie letter from the Secretary of the Stalham 
Farmer's Club. 
The soils, from the presence of the alkalies and alkaline earths, and of 
all the proper acids, with the exception of phosphoric acid in the subsoil, 
are admirably calculated to furnish plants with their proper food. 
Sir, I have the honour to be. 
Your obedient and faithful Servant, 
Museum of Economic Geology, Craig^s Court, Lyon Playfair. 
Charing Cross, 1th July, 1845. 
XIV. — On the Jerusalem Potato or Artichoke (Helianthus » 
tuberosus). 
[From ' Boussingault's Rural Economy.'] 
"This i)lant is generally believed to be a native of South America, 
but dc Humboldt never met with it there, and according to M. 
Correa, it does not exist in Brazil. The property which the tubers of 
this plant have of resisting the cold of our winters, and several botanico- 
