PREFACE. 
— 
In the publication of the four parts which complete the pre- 
sent volume of the Scientific Memoirs, I have ventured 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 country. 
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, will 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 still 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- 
