282 Mr. Faraday on Chemical Manipulation. 



uncertain concerning many of his former products. This evil 

 is increased, if a new series of operations succeed, and occupy 

 all the laboratory ; or if he be obliged to quit the place for 

 some time, every thing then goes into confusion. Hence it 

 frequently happens that he loses the fruits of much labour, 

 and that he must throw away almost all the products of his 

 experiments. 



" The only method of avoiding these inconveniences is to 

 employ the cares and attentions above mentioned. It is 

 indeed unpleasant and very difficult continually to stop in the 

 midst of the most interesting researches, and to employ much 

 valuable time in cleaning and arranging vessels and attaching 

 labels. These employments are capable of cooling and re- 

 tarding the progress of genius, and are tedious and disgust- 

 ing ; but they are nevertheless necessary. Those persons 

 whose fortunes enable them to have an assistant operator, 

 on whose accuracy and intelligence they can depend, avoid 

 many of these disagreeable circumstances ; but they ought 

 nevertheless to attend to the execution of these things. We 

 cannot depend too much on ourselves in these matters, how- 

 ever minute, on account of their consequences. This be- 

 comes even indispensable when the experiments are to be 

 kept secret, at least for a time, which is very common and 

 often necessary in chemistry. 



*' When new researches aud inquiries are made, the mix- 

 tures, results, and products of all the operations ought to be 

 kept a long time well ticketed and noted. It frequently 

 happens that at the end of some time these things present 

 very singular phenomena, which would never have been sus- 

 pected. There are many beautiful discoveries in chemistry 

 which were made in this manner, and certainly a much 

 greater number which have been lost, because the products 

 have been thrown away too hastily, or because they could 

 not be recognised after the changes which happened to 

 them." 



The uses of equivalents, and the method of employing Dr. 

 Wollaston's scale, form the subject of the twenty-second 

 section of Mr, Faraday's book ; and of the concluding sec- 

 tions, the twenty-third contains a quantity of miscellaneous 

 remarks, and the twenty-fourth is appropriated to '* a course 

 of inductive and instructive practices ;" that is, to a selection 

 of minute instructions respecting the use of instruments, and 

 the performance of operatioUvS. 



Such is an outline of the contents of this volume, of which 

 we have felt ourselves obliged to speak in terms unequivocally 



