ADVERTISEMENT. 
Ax the close of his former publication, the 
Author intimated his intention of prosecuting 
his inquiries, if the public approbation of his 
labours should be such as to encourage their 
continuance, and future experience should ap- 
pear to confirm his views. An interval of four 
years has now elapsed since the date of his former 
Work, during which period many important addi- 
tions have been made to the various branches 
of research connected with the subjects discuss- 
ed in this volume; and the new views, which 
the late discoveries of Mr Davy have introduced 
into Chemical Science, may also be expected to 
extend their influence to all its Physiological ap- 
plications. From these causes, joined to the 
Author's endeavours to correct some of his for- 
mer opinions, and to illustrate and improve 
others, the additions which he now brings forward, 
have insensibly acquired a size greater than that 
of his original Work. 
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