190 Bibliography. 
urgent, and in that country acquires.a vastly superior importance. When a tract 
of land i is thinly peopled, like the newly settled districts of North America, New 
ed, its special qualities and defects must be studied, and means must gradually be, 
adopted for extracting the maximum produce from eyery portion susceptible of 
cultivation.” 
The British Islands are in the latter condition. _ Supposing capaaia 
tion from abroad not to have increased to any important extent, it ap- 
pears that the soil of Great Britain has, by improved management, been 
made to yield twice the quantity of food it afforded half a century ago}; 
ural interest in 
attempting to secure or maintain important political aicaiaeees in the 
state, might with propriety be devoted to the encouragement of experi-. 
mental agriculture. ‘The suggestion is as important as itis mesuts 
After presenting a plain account of the difference between simple and 
compound bodies, organic and inorganic matter, and_ briefly —— 
the properties of the four organic elements of plants, viz. carbon, oxy- 
gen, hydrogen and nitrogen, Prof. Johnston concludes his first lectins 
with the following remarks : 
“Such are the several PBL bodies of which the organic or senizcasie 
part of vegetable substances is formed. With one exception they are known to 
us only in the form of gases ; tine we out of these gases much of the solid parts 
ce and of plants are made up, When alone, at the ordinary tem; mperature 
Pc gat they form invisible kinds of air ; when united, they constitute 
various forms of vegetable matter which it is the aim and end of the art 
poe awrite ene: with certainty, and in abundance. How difficult to 
understand the intricate processes by which nature works up these raw materials 
into her many ‘beautiful ion t how interesti 
ways, how useful even partially to to find them out! Permit me, in conclusion, t0 
submit to you one reflection. We have seen that oxygen, hydrogen, and nitrogen, 
are all gaseous substances, which when pure are destitute of color, taste, am 
smell. ‘They 8908 be distinguished: by the aid of our senses. Man in a state of 
e—uner —cannot diseern that they are different. Net so simple 
ani instrument sigh taper at once shows them to be totally unlike each other. 
This si th re, Serves us instead of a new sense, and makes Us_ 
the-existence of which, without such aid, we should not 
