36 
EXTRACTS — HORTICULTURE. 
bility of taking up and retaining water. ' Compost heaps must be managed on 
the general principles of chemistry already detailed, particular care being taken 
to guard against loss. Lime, for example', if mixed in a compost heap with rich 
old soil, or with rotten dung, will take up and render useless the carbonic acid 
gas which they contain, and can only be where there is much wood}" fibre dif 
ficult to be broken down. Bog earth mixed with fermenting dung, forms a good 
compost, as does also all vegetable refuse, such as weeds, young shoots of trees, 
and turf Irom hedge banks, or road sides.” 
EXTRACTS. 
HORTICULTURAL INTELLIGENCE. 
Experiments on Gases Hurtful to Vegetation. —Some plants of Eu 
phorbium, Mercury, Groundsel, Cabbage, and Sow-thistle, with their roots, were 
placed, by Mr. Macaire, of Geneva, in the morning, in a large vase, into which 
chlorine of lime had been introduced. The roots were then separately soaked, 
and the quantity of chlorine disengaged was by no means sufficient to impair the 
vegetable tissue. At night, the plants had not suffered, and the smell of the 
chlorine was unchanged. The same plants, placed in the same vase, without 
any addition of chlorine, were found quite faded the next morning, after conti¬ 
nuing all night, with the exception of the cabbage, which had resisted it. The 
odour of the chlorine had entirely escaped, and had been succeeded by a disa 
greeable acid smell. The experiment being several times repeated, by rendering 
the extrication of chlorine more considerable, produced the same result, and the 
plants supported an atmosphere strongly impregnated with chlorine by day, while 
a much weaker dose always destroyed them during the night. 
Nitric Acid .—The experiment which was commenced at night, like the preced¬ 
ing, with vapours of Nitric Acid, exhibited the. plants faded in the morning, but 
some leaves were wrinkled by the action of the acid. The same dose was tried 
by day, and although several leaves were wrinkled, the others were not at all 
withered. 
Nitrous Acid Gas .—This gas appears to be a violent poison for plants, and a 
very small dose will kill them at night.. By day, however, they do not appear 
to be sensibly affected, although the extrication of the gas may be abundant. 
Sulphurated Hydrogen .—Precisely the same result. The plants were left at 
night in the same mixture of gases, which had not in the least changed them 
while in the light. They were all faded in the morning, and the gas absorbed; 
the cabbage alone resisting. 
Muriatic Acid Gas .—The same results. The plants did not perish in the day, 
even when the quantity of gas was sufficient to wrinkle one or two leaves: they 
were quite dead in the morning, again leaving that particular odour already 
mentioned, excepting the cabbage. It appears by these trials, that many of the 
gases are hurtful to vegetation, but that they acton them only during the absence 
of light.— Mag. Bat. and Gard. 
How far Marl contributes to the fertility of soils. 1st. Not materially, for it 
is devoid of every unctuous and saline matter. 2ndly. But instrumental!)’ it 
