420 
Farming of Cornwall. 
formation will let at 40^. to 45y. per acre. The farmers de- 
signate it by the name of " Marie-soil," arising from their using 
as a manure this rock in a decomposed state, in which state it is 
found to a very great depth. The system of cropping is wheat, 
oats, turnips or potatoes, barley and seeds, laid down for three 
years. The wheat averages 34 bushels, barley from 40 to 48 
bushels, oats from 80 to 96 bushels, and potatoes from 250 to 
300 bushels per acre. {See analyses of this soil — 16.) I would 
recommend the farmers in this locality to grow the early spring 
potatoes, which produce such a profitable return in the London 
market. The soil is similar to that of Penzance, with a climate 
in most places near the sea equally mild. On Trevean estate, in 
St. Keverne, this has been practised successfully. 
31. Diallage Soil. — The rocks of this formation are chiefly 
confined to the borders of Crousa Downs (see section). They 
are massive and crystalline, projecting at the brow of the hills in 
immense blocks piled one over the other, and strewed on the 
sloping ground beneath, giving to the whole scene an extremely 
wild and rugged appearance. The rock is of a very Protean 
character, by some called syenite, and said to be composed of a 
coarse mixture of felspar, hornblende, and diallage. Sir H. T. 
De la Beche is of opinion that only a portion of this formation 
can be so considered, whilst the greater part is a true diallage. 
Of course the relative fertility of this soil will chiefly depend on 
the proportion of hornblende which enters into its composition.* 
Some of the land is let at 28s. per acre. The system of cropping 
is similar to that on the hornblende, but the yield is not so great. 
Wheat averages 24 bushels, barley 36 bushels, oats 70 bushels, 
potatoes from 200 to 250 bushels per acre. Farmers in the 
Meneagc district breed few cattle or sheep, purchasing their stock 
at the eastern fairs and fattening for the butcher. Pigs are reared 
in immense quantities, averaging from 25 to 30 per cent, on the 
acreage. The remainder of the Meneage district lying on the 
slate formation is of the ordinary character, everywhere improved 
by the masses of greenstone which it intersects. 
32. I have included in this survey every description of soil, 
and with the exception of some coarse land situate on the slates 
round or near the granite outbursts, almost every parish in the 
county. Those situate in the parishes of Germoe, Breage, and 
* Mr. Whitley, in his ' Agricultural Geology,' gives the following ana- 
lysis of this rock, when it is composed of two-thirds felspar and one-third- 
hornblende : — 
Silica 56-0 
Akimina 
Magnesia 
Potash and Soda 
Lime 
Oxide of Iron . 
17-0 
(iO 
120 
40 
50 
