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TRANSACTIONS OF THE SECTIONS. 117 
MECHANICS. 
Mr. J. Asuman exhibited an artificial leg, of an improved construction. 
On Improvements in the Reflecting Circle, more particularly in reference to 
an instrument for the purpose of measuring angular distances of the Sun 
and Moon. By J.C. DENNIS. 
So great is the accuracy required in instruments of this kind that it is necessary 
to distinguish to the 5940th part of an inch. The smallest error of construction 
therefrom produces a serious error in the observation; and to render the construc- 
tion more perfect, the following suggestion is made :—Instead of attaching the circle 
(technically called an arc) to the parts which support it, let the whole be cast in one 
piece, and then planed, polished or divided, to suit the purposes of modern astro- 
nomy. 
"On the application of Steam Power to the Drainage of Marshes and Fen 
3 Lands. By JosEru Giyyn, F.RS., WM Inst. CE. 
___ The steam-engine is used to raise the water above the level of those lands which 
4 lie too low to be drained by natural outfall, and also in situations where the fall is not 
_ sufficient to carry off the superfluous water in time to prevent damage to the crops. 
_ Mr. Glynn has applied steam power to the drainage of land in fifteen districts, all 
_ in England, chiefly in Cambridgeshire, Lincolnshire, and Norfolk. The quantity of 
land so drained amounts to more than 125,000 acres, the engines employed being se- 
_ venteen in number, and their aggregate power 870 horses ; the form of the engines 
varies from 20 to 80 horses. Mr. Glynn was also engaged in draining by steam power 
_ the Hammerbrook district, close by the city of Hamburg ; and in another level near to 
Rotterdam, an engine and machinery with the requisite buildings have been erected 
- from his plans, by the Chevalier Conrad, and the works successfully carried into effect. 
_ In British Guiana the steam-engine has been made to answer the double purpose 
of drainage and irrigation. Some of the sugar-plantations of Demerara are drained 
_of the superfluous water during the rainy season and watered during the dry season. 
In many of the swampy levels of Lincolnshire and Cambridgeshire much had been 
done to carry off the water by natural means, and many large cuts had been made and 
embankments formed, especially in the Bedford Level, which alone contains about 
300,000 acres of fen-land; the Great Level of the fens contains about 680,000, for- 
_ merly of little value, but now rich in corn and cattle. 
Tie Dutch engineers, who were at an early period engaged in these works of 
drainage, had erected a great number of windmills to raise and throw off the water 
yhen the sluices could not carry it away. By the aid of these machines the land was 
‘so far reclaimed as to be brought into summer pasture and a precarious state of cul- 
vation producing occasionally crops of wheat. The waters from the uplands and 
ligher levels were intercepted by catch-water drains, which carried away the high- 
land waters, as far as might be practicable, and prevented them from running down 
upon the fen, from which the excess of rain-water was lifted by the mills. But, as it 
| often happened, when there was most rain there was least wind, so that the wind- 
‘engines were often useless when their help was most needed, and the crops were 
consequently lost. 
In this state was the fen-country when the steam-engine was introduced, and by its 
| aidthe farmer may now venture to sow wheat with as much confidence, and even more, 
| than upon higher ground ; for not only can he throw off the superfluous water at 
| pleasure, but in dry weather a supply can be admitted from the rivers, so that farm- 
‘ing in such situations is rendered less precarious than in situations originally more 
favoured by nature. 
It is however to be remarked, that the quantity of rain which falls on those levels 
on the eastern side of England being much below the general average of the kingdom, 
the power required to throw off the superfluous water is small when compared with 
§ 
