Perspective Instrument . 26 & 
If the distance between any two points on the shore be 
measured, it will give you a scale for the plan ; but it may 
often be found more convenient to measure off a base, as 
AC, from one of the stations, in a direction nearly per- 
pendicular to the line AB ; and let it be in length equal 
to some part of a geographical mile, as 380 feet = T \, 
or 760 = 1 , or 1520 = i or 3040 = |, or any part of a 
mile; then will the line AC be a scale to the plan. 
I have supposed any common board and ruler to illus- 
trate the simplicity of this method of surveying : but to 
such as are provided with a drawing frame, it will be 
found convenient to extend the paper on; and if a rule4 
has sights perpendicular to its edge, it will be found com- 
modious, and require less trouble. I hope the ease and 
expedition with which the whole is performed, will in- 
duce sea-faring people to amuse themselves by taking 
plans of the places they touch at : for it is by the im- 
provement of geography that the dangers of navigation 
are diminished, and, consequently the lives and property 
embarked in our shipping are less exposed to danger. 
No. 53. 
Description of a simple Instrument for making correct 
Drawings from Nature. By T. C. B.* 
(With an engraving’.) 
SIR— The description of two instruments for facili- 
tating landscape drawing from nature given in the first 
volume, page 281, of your Journal,! has suggested to me 
the construction of another, which seems to unite the ac- 
curacy of the first of those instruments with the simplicity 
and portability of the second. As I conceive it may be 
* Nicholson, vol. 10, p. 111. 
f See p. 258 of this volume of the Emporium. 
VOL. II. K k 
