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· Also, with respect to the food of animals, chemistry points out what particular food is best fitted for a required purpose; the proximate principles of fleshy matter, such as form the muscles, fat, etc., are formed in the plants ; the stomachs of animals dissolve the compound substances into their proximate principles, they circulate through the blood, and are thus assimilated to the different parts of the body. : For instance, the farmer wishes the calf, the lamb, or colt, to become a well-grown animal, to have muscle, bone, and sinew; the cow to give milk which will yield a great deal of butter and cheese, excepting in large towns, where they want quantity and not quality; the ox he wants to feed on such substances as will leave the most of fat on his bones.
In all these cases, from knowing the composition of the different vegetable substances, such as turnips, swedes, inangel-wurzel, different kinds of hay, etc., there is something of a guide as to what plants would be best suited for any particular purpose.
The farmer knows that one grass field is better than another for young stock, for milk, for fattening, etc., which is nothing more than that the grasses in one field are of that kind which have more in them of those substances of which bone, or muscle, etc., is made---in another more of the substance of milk and in the third of fatty matter ; here experience has taught that which science would confirm, if the agricultural chemist were to analyse the grasses which most abound in such pastures.
Calling attention, also, to the influence of light-heatmoisture, etc., in the atmosphere-wet and cold seasons, etc., on vegetatiun--that a great deal of rain has a tendency on many soils to produce more straw in our cereal crops than dry weather, etc.; in fact, calling the thinking faculties of man more into action in the business of agriculture ; and not making it in the same degree that mechanical routine sort of thing which of all other occupations carried on in this country it has hitherto been ; and thought to require less of intellect than anything else. Of all occupations it is that which is most natural to man, and that without which we cannot exist.
When a knowledge has been obtained of the simple ele. ments of which vegetable matter is composed, and of the substances, starch, gluten, oil, or fat, and inorganic matter, which a healthy animal ought to derive from its food, it will be found useful and instructive to call attention to the ascertained quantities of each of these in given weights of particular kinds of grain—or other substances of a nutritive kind, such as the following:-
According to Johnston, in his “ Chemical Catechism," “ 100 lbs. of wheaten flour contain about 50 lbs. of starch, 10 lbs. of gluten, and 2 or 3 lbs. of oil.
“ In 100 lbs. of oats there are about 60 lbs. of starch, 16 lbs. of gluten, and 6 lbs. of oil.
“In 100 lbs. of potatoes, about 75 lbs. of water, and from 15 to 20 lbs. of starch ; and in 100 lbs. of turnips there are about 88 lbs. of water.
" And of animal substances, 100 lbs. of butter contain from 10 to 12 lbs. of water, about 1 lb. of curd; the rest is fat.
« 100 lbs. of cheese contain from 30 to 45 lbs. of water: skim-milk cheese from 6 to 10 lbs. per cent. of butter; full-milk cheese from 20 to 30 lbs. per cent. of butter, and about as much pure curd.”
Tables, also, similar to the following, connected with the chemistry of food and of nutrition, and which is taken from Brandt, may be made a means of suggesting most useful observations. This shows the change which takes place in the proximate elements of barley, in the process of malting :
Composition of Barley.
of Malt. Starch
The most remarkable change being of a large quantity of starch into the substances sugar and gum.
The following, shewing the functions of animals and vegetables, suggests many useful hints :
AN ANIMAL IS AN
, ammonia Exhales carbonic acid
gum, alcohol, etc.
oxygen Produces heat
, electricity Restores to the air and earth
its elements Changes organised into mineral
An exact knowledge of the nutritive properties of vegetable substances— food for man and beast and the exact proportions, both quantitative and qualitative, in each, is of great importance to an agricultural people, as having a tendency to induce them to cultivate the most nutritive kind; and one can scarcely conceive a people having such knowledge, and bringing their mind to bear upon it-cultivating, for instance, the potatomas food for man-considering also its perishable nature, to the extent which the Irish have done, in preference to crops of a cereal kind.
That great permanent benefit will be conferred upon the farming classes by the introduction of such instruction into our schools, there can be no doubt, not only in an increase of produce arising out of improved modes of culture as regards the soil, but, in addition to this, it will lead to an improved culture of the mind in the rising generation of
agricultural youth, and make them, as a body, a much more intelligent class of men than they are at present.
The following table, which is an analysis by Dr. Lyon Playfair of different kinds of food, and the coloured diagram in the frontispiece constructed from it, offer most useful hints not only on the properties of food, but on illustrative modes of instruction. They also show how a mixed diet may be both more nutritive and healthy than one which is confined either to animal or to vegetable substances only.
The coloured table will give at a glance an idea of what
Substances used in
.66 1.00 1.00 *08 .62
is meant; and the more exact proportions will be learned by the decimal points in the table.
This table and the diagram may also suggest more exact and instructive methods of teaching other useful lessons, which a teacher might wish to bring before his school. It
is, I believe, the intention of Dr. Lyon Playfair, secretary to the Board for the encouragement of Science, under the Board of Trade, to have the table in the frontispiece, with other similar ones on a larger scale, prepared for the use of schools, to be supplied to them at one half the cost price.*
The village schoolmaster who attempts anything of this kind should, in addition to a general knowledge of the particular substances which constitute the ordinary crops, be able to manipulate in a few of the common routine things in general chemistry—in making the ordinary gases, hydrogen, oxygen, carbonic-acid gas, etc.—to show that this last is not a simple but a compound substance, and constitutes nearly one half of all the chalk, limestone, marbles, etc., on the earth ; shew the weight of a piece of chalk or limestone before and after being burnt into lime-the different specific gravities of the gases—that one is combustible- another is a supporter of combustion, and to such a degree that iron will burn in it—that carbonic-acid gas extinguishes flame, destroying animal life when breathed into the lungs-danger of sleeping in a close roon where charcoal is burning, or near a lime-kiln, etc. To show that all these, although the same to the eye, may in other ways be tested and made out. That ammonia consists of two gases, nitrogen and hydrogen, and how formed in the decomposition of plants and animals.
The quantity of carbonic-acid gas locked up in every cubic yard of limestone has been estimated at 16,000 cubic feet. The quantity locked up in coal, in which its basis, carbon, forms from 64 to 75 per cent., must also be enormous ; if all this were set free, extinction of animal life, etc. ; to suggest any mode of approximating to the weight of carbonic-acid gas locked up in a given weight of chalka cubic foot for instance-by weighing it before being converted into lime and weighing it afterwards — difference in weight arising from the gases driven off.
Five per cent. of this gas in the atmosphere would be * This has been done ; and very admirable diagrams, illustrating this and other subjects, are now to be had from the Board of Science and Art : a list of them is given in the Appendix.