PREFACE. 



In the publication of the four parts which complete the pre- 

 sent volume of the Scientific Memoirs, 1 have ventui-ed to make 

 the experiment how far I might be able to succeed in supplying 

 an auxiliary which, as was stated in the Advertisement prefixt to 

 the First Part, appeared to be much needed for the progress and 

 advancement of science in this countiy. 



My own conviction of the utility of such a work has been 

 much strengthened since I have been engaged in it, both by 

 the importance of the materials that present themselves, and by 

 the expressed opinions of persons most competent to judge. 

 How great indeed the disadvantage must be, under which those 

 are placed who are engaged in any branch of scientific inquiry, 

 from being uninformed as to what is doing, or has been done, 

 by our active and laborious neighbours on the Continent, must 

 be obvious to every one : and the cases are numerous to which 

 the remark of Lenz, p. 312, speaking of Ohm's theory of the gal- 

 vanic battery, Avill apply,— that, although given to the world 

 several years ago, yet, " being only published in the German 

 language, it is unknown both in France and in England." 



With regard to the execution of the work, I must submit it 

 to the candid judgement of those who are aware of the difficulty 

 of the task,— having availed myself of the valuable suggestions 

 with which I have been favoured in the selection of memoirs, 

 and of the best assistance within my reach for their translation. 

 I shall be satisfied if what has been done should render the 

 present volume useful to science, and if what there is stiU to 

 do should induce the public to enable me to continue the work. 

 Hitherto, as I can hardly yet boast of the sale of 250 copies, I 

 am very far from having been repaid the cost of publication, to 

 say nothing of the care and labour which have been required: 

 nor could I be expected, having now finished a volume, which, 

 from the nature of its materials, may be considered a complete 

 work in itself, to proceed further unaided, until I have ascer- 



