General Notices. 563 



Subsoil-Ploughing and the Frequent-Drain System. — The advantages of these 

 practices have lately been scientifically explained by a most intelligent and 

 judicious writer, in the Quarterly Journal of Agriculture, vol. x. p. 131.; and 

 the following may be considered the essence of the article, though to be pro- 

 perly impressed with its importance, the reader ought to peruse the five pages 

 which it occupies. The subsoil in a great many instances abounds in oxide of 

 iron, which, when perfectly dry, is insoluble, and consequently not injurious to 

 vegetation ; but when it is soaked in water it becomes to a certain extent 

 soluble, or what in chemical language is termed a hydrate, and in that state it 

 is extremely injurious. Now, the great benefit attending the frequent or the 

 furrow drain system consists in its withdrawing the water from this hydrate, 

 so that it may no longer be soaked in it ; and the great benefit of subsoil- 

 ploughing results from the hydrate being raised to the surface, exposed to the 

 air, broken in pieces, and mixed with the soil, so as no longer to be injurious. 

 Without underdraining, where the subsoil consists of hydrate of iron, subsoil- 

 ploughing will be of little or no use ; but with it the worst lands, by the aid of 

 lime and manure, may in a short time be rendered almost equal to the best. 

 The presence of iron in the soil, whether in the state of oxide or hydrate, is 

 easily known to practical men by its rusty brown colour. In every soil iron is 

 present in a greater or less degree, but only injurious when it is in a state of 

 hydrate. In all other states it is insoluble, and therefore harmless to plants. 

 (Quarterly Journal of Agriculture, vol. x. p. 131.) 



Black, the very worst Colour for painting Woodwork in the open Air. — There 

 is nothing that will prove this evil more than by observing the black streaks 

 of a ship after being in a tropical climate for any length of time. It will be 

 found that the wood round the fastenings is in a state of decay, while the 

 white work is as sound as ever ; the planks that are painted black will be 

 found split in all directions, while the frequent necessity of caulking a ship in 

 that situation likewise adds to the common destruction ; and I am fully 

 persuaded that a piece of wood painted white will be preserved from perishing 

 as long again, if exposed to the weather, as a similar piece painted black, 

 especially in a tropical climate. 



I have heard many men of considerable experience say that black is good 

 for nothing on wood, as it possesses no body to exclude the weather. This is, 

 indeed, partly the case ; but a far greater evil than this attends the use of 

 black paint, which ought entirely to exclude its use on any work out of doors, 

 viz. its property of absorbing heat. A black unpolished surface is the greatest 

 absorber and radiater of heat known; while a white surface, on the other 

 hand, is a bad absorber and radiater of the same; consequently, black paint 

 is more pernicious to the wood than white. Wood having a black surface 

 will imbibe considerably more heat in the same temperature of climate than if 

 that surface were white; from which circumstance we may easily conclude 

 that the pores of wood of any nature will have a tendency to expand, and 

 rend in all directions, when exposed under such circumstances ; the water, of 

 course, being admitted, causes a gradual and progressive decay, which must be 

 imperceptibly increasing from every change of weather. The remedy to so 

 great an evil is particularly simple, viz. by using white, instead of black paint, 

 which not only forms a better surface, but is a preventive to the action of 

 heat, and is more impervious to moisture. The saving of expense would also 

 be immense, and I am convinced that men of practical experience will bear me 

 out in my assertion. (Trans. Soc. Art., as quoted in the Civil Engineer, vol. ii. 

 p. 189.) The writer next goes on to describe the effect on two ships of war, 

 in which all the external parts painted black were in a state of decay, while 

 the parts painted white were as sound as ever. — Cond. 



The Improvement of Harbours and of Drainage by Rivers depends on the 

 management and direction of natural causes and effects, in which, I may say, 

 observation had been so torpid, that, till twenty years since, much more harm 

 than good had been the result of interference. All the reports of Mr. Smea- 

 ton, and some made scarcely sixteen years since, prove that in large drainages 



