118 
part of their constituents ; they appear to us as far as our ob- 
servations and their changes go, to act only by their presence. 
The instances which Mr. Everitt cited in illustration of this class 
of phenomena, were the conversion of starch into sugar, merely 
by its being boiled for a few hours with water slightly acidula- 
ted with sulphuric acid, which acid, after it has effected the mo- 
dification, is found in a perfectly uncombined and unaltered 
state, and can be removed by chalk, the sugar being then left 
alone in solution. A similar action is effected by the same 
agent on the fibres of wood or lignin ; thus if linen be cut into 
very small pieces, and oil of vitriol dropped on little by litlte, 
carefully stirring the whole to prevent the temperature rising, 
afterward rubbing the mass in a mortar, it soon loses its fibrous 
character and becomes homogenous, and cpiite soluble in water, 
from which if we remove the acid by chalk and evaporate to 
dryness, we obtain a substance exactly similar to gum arabic. 
If, previously to removing the acid, the solution be kept at 212 
degrees, or the boiling point of heat, for thirty or forty hours, 
and then the acid be removed as before, in lieu of gum we have 
sugar, like that obtained from the starch. Here, as in the other 
case, no part of the acid has disa]ipeared or been destroyed. 
Another instance is the conversion of sugar, when dissolved in 
water and the solution kept at a certain temperature, into alco- 
hol and carbonic acid, by the presence of a little ferment or 
some few other matters. The conversion of alcohol into ether 
and water has been proved to be a similar case, it having been 
shewn that a definite quantity of sulphuric acid, properly dilu- 
ted with water, and the process managed in a peculiar way, was 
capable of etherifying any indefinite quantity of alcohol.” 
152 Garden Walls. We have, previously, had occasion to men- 
tion, in terms of commendation the straight-forward directions 
contained in a little work — Rogers’s Fruit Cultivator. From 
this we copy the following observations, “ Garden walls are 
usually built higher or lower, according to the size of the gar- 
den itself. From eight to ten feet from the offset at the bot- 
tom, to the underside of the coping, is height enough for a 
garden containing from two to four acres. Garden walls have 
been built on arches, for the purpose of allowing the roots of 
the trees to extend themselves in all directions; but this can 
answer no good purpose, because their is quite scope enough 
