564< General Notices. 



near the sea, natural outlets or rivers were always recommended to be stopped 

 by dams and sluices, to prevent the tide from entering, which obstacles equally 

 prevented the drainage water from free passage outward. 



Three inches fall (downward slope) in a mile makes water move slowly; at 

 four inches declivity in a mile, water acquires a moderate velocity, sufficient 

 for any drainage operation ; so that the sill (threshold) of a sluice, if laid a 

 yard too high, will prevent the natural drainage of twelve miles above it 

 (3 in. to a mile) : on the same principle, if a drainage outlet, obstructed by 

 what may be almost deemed the caprice of winds and tides, and of accumu- 

 lated sand-banks in consequence, shall double its length, and creep through a 

 dubious crooked channel, it is evident that a 3 in. or 4 in. fall may become 

 1 in., which is ineffectual. 



The sound principle which results from these facts is, to give free ingress to 

 the tidal water, guarding against inundation by raising the banks of your river, 

 and also straightening its course, so as to lose no downfall. This increased 

 downfall and increased tidal water are made to bear directly upon the old sand- 

 banks ; and, if the connexion with deep water can be established in this man- 

 ner, you obtain a harbour of easy access, and the old-fashioned precarious 

 drainage of land by windmills becomes unnecessary, the dams which previously 

 hindered daily drainage at low water being for ever removed. 



All this was to be seen in progress below Wisbeach and Long Sutton Bridge, 

 and the impetuous outfall of the water in the recess of a spring tide had 

 forced its way through the sands in the beginning of August, 1830. With a 

 view to this event, the old channel of the river Nene had been boldly dammed 

 across in the middle of July, and the current turned into the straight cut pre- 

 pared for it. All this constitutes the Nene Outfall. When I saw it meet 

 the sea, four miles below the washway (now the drawbridge at Long Sutton) 

 at three-quarters ebb, the torrent rushed down 4 ft. in the last quarter of a 

 mile. This, of course, carries off the sand daily, and, by the law of nature, the 

 4 ft. fall will recede inland, until nearly a uniform inclination or slope shall 

 penetrate to Wisbeach, which will become a seaport of importance ; and, above 

 it, 180,000 or 200,000 acres of fen land will retain nothing of its hitherto 

 nature, except unparalleled fertility. {Quarterly Review, vol. lxiii. p. 450. 

 No. cxxvi. March, 1839.) 



From the above extract, the young gardener may learn to assign a scientific 

 reason for straightening crooked brooks, when the object is to make them run 

 quicker, or rendering straight ones circuitous, when it is desired to cause a rapid 

 stream to be less so. By reflecting on the extract, he will find other matters 

 from which he may benefit, but which, lest we should prevent him from seeking 

 and thinking for himself, we shall not point out. — Cond. 



Warming and Ventilating. — The Telford medal has lately been awarded to 

 Mr. Charles Hood, F.R.A.S., for an article on this subject, of which an 

 abstract is given in the Athenceum for July 13. The author, after showing the 

 defects of iron stoves of every description, recommends, as the best mode of 

 heating, steam or hot water in iron pipes. These are " more economical and 

 simple, present greater permanence and equality, and a lower uniform rate of 

 temperature, and admit of any form of heating surface. The temperature of 

 the metallic surface rarely exceeds 180° Fahr., and never reaches 212°, which 

 is too low to decompose in any appreciable degree the organic matter contained 

 in the air. The only effect is to increase the capacity of the air for moisture, 

 which is readily obviated. The surface which is intended to distribute the 

 heat should be a good conductor and radiater, and the material which presents 

 this combination in its highest degree is iron. The amount of heating surface 

 which will be required depends on the building to be warmed, and on a great 

 variety of circumstances ; but, as an approximate rule, it may be said, that for 

 a church or similar public building, the cubic contents of the building divided 

 by 200, will give the number of feet of surface requisite for a temperature of 

 from 55° Fahr. to 58° Fahr. in the coldest weather ordinarily experienced in 

 this country. The form of the heating surface is immaterial as regards the 



