MECHANICS AND USEFUL ARTS. 35 



Austerlitz, a ship-of- the- line of the same class, then on the stocks at Cher- 

 bourg ; but after the maturest consideration, the constructors and engineers 

 were compelled to decide that this could not be done under any reasonable 

 conditions ; that it would be necessary to cut her in two and lengthen her 

 floor ; that her stern must be taken down and rebuilt ; and that, after all, 

 these great and expensive alterations promised no satisfactory result. 



In consequence of the unfavorable report of the officers upon this sub- 

 ject, the minister of marine directed that an engine of five hundred-horse 

 power should be substituted for that of six hundred and fifty-horse power, 

 which it had been intended to place on board the Austerlitz, in order to 

 ascertain if, with this less powerful engine, and without any reduction in 

 her battery, spars, or other equipment, it was possible to attain a speed of 

 not less than four and a half knots under steam. 



The attempt has been made to execute the order of the minister ; the 

 stern of the ship has been entirely rebuilt, (with the addition of a " trunk " 

 or "well,") at the cost of 400,000 francs, and on the 14th of September, 

 1842, she was launched; but it was found quite impossible to comply with 

 all his requirements in relation to the armament and equipment of the ship. 



I cannot, of course, give any very minute detail of those particulars in 

 which it was found necessary to deviate from the plan of the government, 

 but I have ascertained that her battery has been reduced to eighty- eight 

 guns ; that her munitions of war have been diminished one-fourth part ; 

 that her spars and sails have been cut down to those of a sixty-gun ship ; 

 that she cannot now stow more than one month's water and two months' 

 provisions ; and that she has been so lightened by the removal of one 

 hundred tons of ballast and eighteen tons of cables and anchors, as to 

 render her stability under sail, after the consumption of her coal, highly 

 problematical. 



ON AN INSTRUMENT FOR TAKING SOUNDINGS. 



The following communication from the Philosophical Magazine, (vi. 344,) 

 is by F. Maxwell Lyte, Esq. 



I see, from what Dr. Scoresby has brought before the Association at 

 Hull, that there seems to be some difficulty about obtaining correct sound- 

 ings in places where the currents are strong and flow in different direc- 

 tions at the different points of depth, causing the line to assume different 

 curves in its descent ; and when it comes to be measured over, after the 

 weight has reached the bottom and been hauled up again, the measure- 

 ment gives no approximate idea of the real depth. Now it is plain that 

 this mensuration of the depth of water might be as well made by estimat- 

 ing its vertical pressure, as, in measuring the height of mountains, we 

 measure the barometical pressure of the air ; and so I would propose to do 

 it by an instrument constructed as follows : 



An accurately constructed tube of gun- metal or brass, or some metal 

 not very easily corrodible by salt water, has a glass tube fitted on to it on 



