Mechanical Science. 221 
says he, “ after having laboured at 300 ancient strong holds, and 
constructed 30 new fortresses ; after having conducted 55 sieges, 
and exposed his person in more than 100 battles, Vauban said 
to Louis XIV., in giving him an account of his inspection of the 
canal of Languedoc, with which the king had charged him, 
‘ Sire, I would give all that I have done, and all that remains 
for me to do, to be the author of a work, so admirable and so 
useful to your kingdom.’ In that country” (England), says 
M. de Pommeuse, “ whatever is admitted to be truly useful, 
is not long in becoming the object of general emulation. The 
example set by the Duke of Bridgewater had soon numerous 
imitators ; and since that epoch, the anxiety to make up for 
lost time has been such, that there exist at present in the British 
isles, 103 canals of navigation, the developement of which 
amounts to 2682 English miles (nearly 1000 leagues). One 
only of these canals (61 miles long) belongs to Ireland ; five, 
which form together 150 miles in length, are excavated in 
Scotland; the others, to the number of 97, cover England alone 
as with a net-work, whose surface is not the quarter, and whose 
population is little more than the third, of that of France. This 
country possesses only six canals of grand navigation, the united 
lengths of which constitute only 150 leagues; and about 20 
canals of secondary navigation, which have not altogether more 
than 100 leagues of developement.” 
The author does not scruple to acknowledge, that his prin- 
cipal object in the first half of the published volume, dedicated 
to the English labours, is to stimulate the emulation of his 
compatriots, and to make them co-operate with government in 
the existing circumstances, where France has much to create 
in this department. The editors of the Bibliotheque Universelle, 
in their account of this work, pleasantly observe, that the author’s 
hope reminds them of a reply made to them in Tuscany, by a 
minister of state of great experience, to whom they extolled 
certain improvements elsewhere introduced, and which seemed 
to them capable of being imitated with advantage in his coun- 
try: ‘ Alas!” said he, “ diseases communicate from people 
to people; but health, you know, is not contagious.” 
4. Description of a Ductilimetre, or an Instrument for com- 
paring the Ductility of different kinds of Lead, Tin, &c., described 
in the Annales des Mines, tom. vii.—This instrument is the con- 
trivance of M. Regnier, and is said to furnish an useful means of 
trying different samples of lead and tin, more especially with a 
view of judging of their fitness for lamination. It consists of a 
mass of iron of a given weight, attached to the extremity of an 
iron lever, thirty inches long. (See Plate I.) The other end of 
this lever is moveable upon a transverse axis. When the ham- 
mer is elevated to a certain angle which may be measured upon 
