1816. ] Scientific Intelligence. 819 
it goes out, and cannot be again kindled. Is it not, therefore, 
possible that this apparent burning of the sub-soil is in fact only 
accomplishing imperfectly what Mr. Vanderstraeten says is per- 
formed every third or fourth year in Flanders. In that country, 
according to him, every third or fourth year the sub-soil, which is 
soaked with the manure that has been laid on the surface, is brought 
to the surface by trenching the whole ground, while that which was 
formerly the surface is converted into sub-soil.. By this method he 
says the necessity of fallowing is saved; for the sub-soil in reality 
lies fallow for three successive years. 
In case our farmers should be tempted to try this experiment, it 
may be proper to mention that the Waes, or the country between 
Antwerp and Ghent, in which Flemish farming has been carried to 
the highest point of perfection, was originally nothing but sea sand, 
and that it has become the rich, light soil, which we find it at 
present, from the great quantity of manure laid upon it, for a period 
of at least three centuries. 
V. Lamp for Coal-Mines. 
(To Dr. Thomson.) 
Pereant qui ante nos nostra invenerint aut dixerint. : 
SIR, 
I again prefix my motto by way of correcting the press of the 
last month. The figure ef the lamp is at once an answer to the 
objection in The Philosophical Magazine, that the tube may re- 
ceive explodible air from a blower, whether the lantern be moving 
or stationary. ‘The safety principle of Sir H. Davy’s lantern was at 
first supposed to be foul air within the lantern derived from the 
combustion of the wick. ‘This was an error; and the diminished 
flame has been shown to be owing to the diminished supply of air. 
At first air was admitted by one or two large holes at the bottom of 
the lantern; explosions took place; to these holes, diminished in 
size, and increased in number, tubes were added. Finally, the 
holes were multiplied until they deviated into gauze. At every 
progressive changé The Philosophical Magazine abused those who 
doubted. If 1am now asked if I trust in the gauze, my reason 
for doubting is the abuse which The Philosophical Magazine con- 
tinues to bestow on all who shall doubt. You have not developed 
the principle upon which the benefits of the gauze depend. You 
talk of a fixedness of the air, which cannot be. If an explosion 
takes place, without any considerable extrication of heat, the con- 
tact of the adjacent wires cools down the red-hot air, and renders 
it incapable of kindling combustion without, This indicates an 
adaptation of apertures and wires, which will vary with the nature 
of the explodible air and the heat developed. ‘There will be, then, 
no safety but what depends upon this due arrangement, and the 
aecess of explodible mixtures not yiglding more heat in combustion 
than is provided. If this heat be in excess, if a stitch be dropped 
