LIFT FOR CANALS. 335 



By comparing the relative quantities of seer- wood contained 

 in a piece of timber while in a growing state, and in the same 

 timber after it has been dried, we may ascertain how much its 

 fabric has shrunk by dessication. 



It appears from these experiments, that the oak sold in the 

 timber-yards of Paris, for fiie-wood, contains rather more than 

 one- half of the sap which it formerly had, in a growing state. 



I have made several similar experiments upon other species of 

 wood 3 but their results are better calculated for exhibition in a 

 table, than for circumstantial detail. 



(To be continue I.) 



III. 



Description of the perpendicular Uft erected as a Substitute for 

 Locks on the Worcester and Birmingham Canal at Tardebig, 

 near Broms grove. By Air. Woodhouse. From a printed 

 Letter of Mr. Edward Smith, of Birmingham! and \he Re- 

 ports of W. Jessop, Esq. 



THE whole of the machinery is under cover ; and we Machinery 

 entered the building at the lower level of the canal, where forrawoi? a«d 

 i J ? r i ii. , t • lowering 



the appearance of a number of large wheels, rods, and chains, boats upon 



seen in perspective, had a very striking and pleasing effect. canals ui(,,ont 

 We walked by the side of an oblong trough or vessel, filled pence of wa- 

 with water, large enough for a canal boat to float in. Tbis ter » by 

 reservoir of water, with the canal boat, weighs sixty-four tons, 

 and is suspended by eight rods and chains over as many large 

 cast-iron wheels or pullies, which are balanced on the other 

 side of the wall by an equal number of square frames, loaded 

 with brick-work, or other heavy materials. After examining 

 the lower structure of the building and machine, we got into 

 an empty boat which floated in the reservoir, and were slowly 

 raised to the upper level of the canal, without any noise or jarring 

 of the machinery, by means of wheels and pinions on the other 

 side, which were worked by two men with great ease ; it took 

 about three minutes to ascend twelve feet, the difference be- 

 tween the two levels. When the trough is thus raised to th« 

 peccssary height, the paddles at the end., which are ingeniously 



con- 



