LECTURES ON CHEMISTRY. 
750 
are visible and others invisible, yet all are made up of a few 
only of these elementary substances, the differences which ap- 
pear depending principally upon the proportions in which they 
are united. When they have performed their uses in these forms, 
they enter into new ones ; so that not a particle of matter is 
ever lost, or has need to be formed afresh. All that exists now 
existed at the creation, and will exist till time shall be no more. 
The beautiful varieties, then, of form and properties which are 
presented to the senses are only the result of an interchange be- 
tween these ultimate particles. 
We have before said, that chemistry teaches us the constitution 
of the earth we live on. Its soil, we perceive, is destined for the 
support of plants — of plants which clothe its surface in rich luxu- 
riance, and it affords them nutriment. These, not possessing the 
power of locomotion, become fit food for the various tribes of 
animals which are placed upon it; and these, in their turn, be- 
come food for him who is proudly styled the Lord of the Crea- 
tion. Hence we perceive the links which run throughout the 
chain of Nature ; and it follows from this, that man, animals, 
and vegetables, are composed of similar materials to those which 
constitute their common parent — earth ; nor is there any diffi- 
culty in ascertaining what these are. But, although the chemist 
may analyse the animal frame, separate its constituents, and 
exhibit them, thus making known their various properties, yet 
he cannot re-unite them , so as to cause them again to exist in the 
state in which they did prior to their disunion. It is alone the 
refined operations of vitality which can effect this. By this is 
at once shewn a clear distinction between the powers of life and 
chemical action. 
We need not confine ourselves to the animal kingdom alone 
as illustrative of our subject : the same reasoning will apply to 
vegetable life. The chemist cannot form a grain of wheat nor a 
blade of grass, yet he can tell you the constitution of each. He 
cannot make a particle of starch or of sugar, although he well 
knows the exact proportions in which the oxygen, carbon, and 
hydrogen, exist in them. Here, then, his power ends. He can 
destroy the form and structure, but not create the substance; and 
he is compelled to confess that Nature, in her operations, pre- 
sents us with one vast laboratory, where mechanism is subservi- 
ent to chemistry ; where this is the agent of the higher power, 
vitality ; and where even this ministers to the more exalted 
faculties of sensation and of intellect. 
We have thus traced the wonderful adaptation of plants and 
animals to each other; and so great, indeed, is this, that the 
one could not exist without the other. But, besides this, there 
