THE YOUNG SCIENTIST. 
47 
figures (2 and 3) are all that are necessary 
to enable us to reproduce the object from 
which they were drawn. The example that 
we have given is, however, probably the 
simplest that could have been chosen, and 
Fig. 1. 
greater complication would have required a 
change in our method of drawing it. 
Suppose that instead of two blocks lying 
one on the other, the object had been a 
block with a hole in it, such as is shown in 
I 
Fig. 2. 
Fig. 4. A plan of Fig. 4 is given in Fig. 
5, but a side elevation of Fig. 5 would 
be Fig. 6. This would give us the thick- 
ness of the block, and as the length and 
Fig. 3. 
width of the hole are shown on the 
plan, it would be easy to reproduce the 
article. Instead of an elevation, however, 
most draughtsmen would give a section of 
Fig. 4. 
Fig. 5, as shown in Fig. 7. This shows the 
block as if it were cut in two along the line 
a, b, and the ends of the solid part of the 
block are seen in section, as it is called. 
The reader will here notice that the lines 
on these different figures run in difierent 
Fig. 5. 
directions. The direction of each line is 
intended to express something. Thus, mere 
shading lines, like those on Figs. 1, 4 and 
6, run either horizontally or perpendicu- 
larly. The lines on sections always run di- 
agonally, making an angle of forty-five de- 
Fig. 6. 
grees with the perpendicular. Such a direc- 
tion of the lines always indicates a section. 
A section must always be carried through 
on a certain line. For example, as previ- 
ously stated, Fig. 7 is a section on line a, b. 
Fig. 4. Everything through which the 
Fig. 7. 
line a, b, passes, is shown in section, as the 
reader will very clearly see. In some cases 
sections and elevations are combined. Thus, 
in Fig. 8, the parts through which the line 
a, b, passes, are shown in section, and the 
parts behind that line, and through which 
it does not pass, are shown in elevation. 
Fig. 8. 
The subject of sections is an important one, 
and will occupy our attention in the next 
article. We would again remind our readers 
that the object of these articles is not to 
teach the art of drawing, but to enable our* 
young friends to understand drawings, and 
work from them. 
