ll hereafter, no doubt, be made, by which many new
truths, both theoretically and practically valuable, are sure to be
elucidated.

We may advert, as an illustration, to the feeding properties of the
turnip. It is usual to reckon the value of a crop of turnips by the
number of tons per acre which it is found to yield when so many
square yards of the produce are weighed. But this may be very
fallacious in many ways. If they are white turnips, for instance,
nine tons of small will contain as much nourishment as ten tons of
large--or twenty-seven tons an acre of small turnips will feed as
many sheep as thirty tons per acre of large turnips. Or if the crop
be Swedes, the reverse will be the case, twenty-seven tons of large
will feed as much stock as thirty tons of small.--(Vol. ii., p. 20.)
Mr. Stephens points out other fallacies also, to which we cannot
advert. One, however, he has passed over, of equal, we believe of
greater, consequence than any other--we allude to the variable
quantity of water which the turnip grown on different soils in
different seasons is found to contain.

It is obvious, that in so far as the roots of the turnip, the carrot,
and the potatoe, consist of water, they can serve the purposes of
drink only--they cannot feed the animals to which they are given. Now,
the quantity of water in the turnip is so great, that 100 _tons
sometimes contain only nine tons of dry feeding matter_--more than
nine-tenths of their weight consisting of water. But again, their
constitution is so variable, that 100 _tons sometimes contain more
than twenty tons of dry food_--or less than four-fifths of their
weight of water. It is possible, therefore, that one acre of turnips,
on which only twenty tons are growing, may feed as many sheep as
another on which forty tons are produced. What, therefore, can be
more uncertain than the feeding value of an acre of turnips as
estimated by the weight? How much in the dark are buyers and sellers
of this root? What wonder is there, that different writers should
estimate so very differently the weight of turnips which ought to be
given for the purpose of sustaining the condition, or of increasing
the weight, of the several varieties of stock? Other roots exhibit
similar differences; and even the potatoe, while it sometimes
contains thirty tons of food in every hundred of raw roots, at others,
contains no more than twenty--the same weight, namely, which exists
at times in the turnip. [