1830 .] 
On the Rent of Land. 
129 
to the right or left of it. No material aid can be derived in depicting such situa- 
tions from shades, because the variation in their intensity cannot be rendered evi- 
dent ; and indeed, generally, dependance cannot be placed on the practice of shading 
as a definite measure of acclivity, for it may be seen experimentally, that we cannot 
command so many various tones as stated by D., inasmuch as the gradation will 
be found too nearly imperceptible between any two of them ; and I should say, that 
instead of ten varieties, we have not more than six. 
Having detailed my objections to the German method, I will add that I am not 
the prejudiced advocate of the pictorial mode, the defects of which have been very 
justly urged by D. ; but I think he has not given it the credit due for two qualities, 
which are never.so well expressed by any other method ; viz. character and form. 
On a full consideration of all the difficulties and objections which have been no- 
ticed, I venture to offer the following plan, as calculated to obviate many, though I 
fear it cannot be thought to include a perfect solution of the whole of them. 
I propose to take the pictorial as the basis of my scheme, but to superadd a prac- 
tice of hatching, which after the German mode, shall furnish a value of the angle of 
acclivity. Instead, however, of determining this value, by the thickness of the 
batches, or the interval between them, I would regulate the length of each hatch by 
a graduated scale, on which each angle should have its length proportionately as- 
signed. The general scale of the map, and the degree of exactness required in re- 
presenting the acclivities, must of course determine the scale for the hatches ; but 
on maps of two inches to a mile, it will be found that 50 feet for an angle of 80°, 
and 850 feet for one of 5°, serve well for the extremities of a scale on which the 
hatches will decrease in length 50 feet for every five degrees of acclivity. The de- 
grees of steepness may thus be easily known ; but there is also another advantage 
resulting from this mode, viz. that the difference of level between auy two points 
may be estimated with considerable accuracy and nearly as much ease as their dis- 
tance ; for it is obvious that each hatch will not only represent an angle, but also the 
altitude due to that angle on the space occupied by the length of the hatch, a table 
of which altitudes (as they are constant) should be attached to the map. 
It will readily he conceived, that in many cases the length of the hatch (or suc- 
cession of hatches) will not exactly fill the desired space : I would meet this diffi- 
culty by introducing in the intervals of the last line, another series of the same 
length, but reaching to the extremity required, thus fig. 1. & 2. a a : 
It is not so easy to provide for another difficulty, which, however, is fortunately of less 
frequent occurrence ; viz. that in which the space to be hatched is too short to 
receive hatches of the length required. It would, in general, be better to use only a 
large scale, in order to escape this case altogether ; but it may, if unavoidable, be met 
by coiling up the hatch, thus fig. 3. a : 
In conclusion, I would suggest that the hatching should, for the sake of distinct- 
ness, hi performed with the crow pen, and only so much shading allowed (on the 
pictorial plan) as may he necessary to distinguish the summits of the hills from 
valleys, and cavities from hollows. 
I am, Sir, your obedient servant, 
Sylhet, 2 3d April , 1830. ^ 
JL 
Vf. — On the Rent of Land. 
To the Editor of Gleanings in Science. 
Sir 
I now beg to he allowed to follow up my letter of November last, (Vol. II. p.30.) 
with a few remarks on what I think the most adviseable method of investing 
capital in agricultural speculations in these parts. 
