l4S Notices respecting New Bonks. 



cent events have unhappily again interrupted, I expected that 

 such a reference might be occasicnallv useful in the shops, and 

 that its defects might easily be pardoned, and hereafter removed 

 by those of our professional brethren who are better acquainted 

 with the application of these substances in the countries refer-' 

 red to. 



" The table of doses has been revised, but not much altered. 

 I stated its necessary imperfections in the former preface, which 

 I shall not again repeat; but I beg leave to ofiVr my opinion that 

 doses can be ascertained by experience alone, and that nothing 

 can he more fallacious than to infer those of compound substances 

 from those of their constituent parts. I have had some little 

 experience upon this subject, and I believe the table to he as 

 correct, jjractically, as the nature of the subject v.ill admit. 

 Many uf the articles, it is true, will allow of increase with per- 

 fect safety bevond the lin)its which are here assigned, especially 

 when they are intended to j)roduce some particular riehnite ef- 

 fects: and upon the whole, general practice mav be thought, in 

 fact, and perhaps wisely, to keep itself below the standard rather 

 than exceed it ; and mv chief object lias been not to lead tlie 

 young practitioner into error by wliat 1 have stated. 



" I have allowed the preface to the first edition to remain un- 

 altered in the present one; and the onlv principle stated therein, 

 which is now superseded, J have marked by inverted commas. 



" I find that some errata exist, particularly in the accents, 

 which easily shift, even after thev have once been right; any 

 others which have struck mv eve on revision I have put together 

 in a table, and if more exist I shall be glad to have them pointed 

 out, and to remove them hereafter. 



" I deem it also of importance here, to recommend to the 

 apothecary a most useful, and indeed necessary, new instrument 

 for the purposes of his profession; I mean Dr. Wollaston's Scale 

 of Chemical Equivalents, described in the Philosophical Trans- 

 actions. 



" In acknowledging with unfeigned gratitude a variety of coir.- 

 munications which I have received respecting the present work, 

 ! cannot but particularize the aid of Mr. Hume, chemist, frt 

 Long Acre, to whose practical skill the committee had repeated 

 occasions to express their obligation. Indeed, I am not con- 

 .scious that in any instance I have purloined the observatiorts 

 of others, or used them without due acknowledgement : if I have, 

 it has not been wilfully done; nor need it have been mentioned, 

 but that this proceeding am I charged withal. And if, as the 

 result of tlie whole, I may fairly reflect hereafter witliin my ow!'. 

 mind, that it has been my lot, in any degree, to contribute to 

 the promotion of a profession of so rriuch importance to man- 

 kind, 



