142 
THE YOUNG SCIENTIST. 
found they were all exactly alike in shape 
and size, and to flute them the same pro- 
cess was again gone through. Having 
gone so far, the next part was to place on 
the top of these pillars, a second piece of 
blackwood. This I did by screwing it on 
the smaller worm chuck, and drilling 
eight smaller holes than those in the bot- 
tom, to receive the top of the pillars, of 
course using the same division, with the 
drill set exactly to the same distance 
from the centre as when drilling the 
lower holes, and upon placing the top on 
its place, found all came square and up- 
right; but upon proceeding I unfortun- 
ately found that I had made my slab too 
thin, forgetting that I wanted the bottom 
of the next tier of pillars to fit in the same 
hole. Here, as in many cases, the fact 
of an error often results in something 
more effective than the original idea 
would have been ; in my case it certainly 
was so. Finding I had no room for what 
I wanted, I was of necessity compelled to 
place the second row of pillars between 
those at the bottom, and cover the holes 
already made with small ivory buttons 
with an eccentric pattern cut on them. 
This turned out very effective. Now the 
second series of pillars I desired to cut 
with a pattern of the same description 
your correspondent desires. Now this 
pattern is called the geometric staircase, 
and does to an extent represent a number 
of discs placed one on the other. To 
produce this, I used the eccentric chuck, 
and I give the setting as nearly as possi- 
ble. The diameter of pillar one-half 
inch, the eccentricity of chuck through- 
out one-tenth. Use a small square chisel- 
tool in the slide-rest one-twentieth wide. 
The milled head of slide-rest must of 
course be set at zero, and this will neces- 
sitate moving it just one-half round, to 
shift the tool exactly its width. Having 
done the first cut, the dividing wheel of 
the eccentric chuck must be turned round 
one division of 96, and by proceeding in 
this way, the result will be what I say, a 
series of discs one on the other, and in a 
spiral form. 
One little difficulty I found from the 
length of the pillars, which had to be 
supported by the poppit head, and when 
the wheel is shifted, a different centre is 
required for each cut. In order to obtain 
this, a flat end must be left, and before 
shifting the wheel for each alternate cut, 
the centre must be withdrawn and then 
replaced. It is rather a tedious job, and 
I for one was very glad when I had 
finished them ; but the result amply re- 
paid me for the trouble.— If. Melvill in 
Forge and Lathe. 

Three Amateur Workers— and What 
They Did— IV. 
BY FRED. T. HODGSON. 
TTAVING described the planes and their 
AJ- uses this far, Mr. Carpenter proceeded 
to explain to the boys how these tools 
were to be kept in order. He struck the 
"starter" on the jack-plane, which 
Fig. 12. 
loosened the wedge and iron; he then 
slackened the screw in the rim and took 
it apart. The cutting part being new, as 
a matter of course it wanted sharpening, 
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Fig. 13. 
i fL 
Fig. 14. 
and as he had purchased an oil-stone 
along with the other tools, he produced 
it, and began to show the boys how to use 
it. EUwood fairly screamed with delight 
when he saw the oil-stone, which was a 
Fig, 12. w w, shows the wedge for adjusting and 
holding the iron, in two views. 
Fig. 13 shows the " double iron " ready to put in 
the plane. The lower iron, a a, is the cutter, and 
the upper one, 6 &. is the cap. This cap serves a 
double purpose ; first, to give the shavings the 
proper direction, and second, when placed close 
to the cutting edge, it prevents the cutter from 
tearing up cross-grained stuff. The two irons are 
