THE YOUNG 
cemented with Canada balsam ; but at 
the best this is only to some extent sub- 
stituting one error for another. 
Measuring Inaccessible Dimensions. 
THE following ingenious "wrinkle," 
which we find in the Millstone, is by 
Mr. John Walker, of Baltimore, and will 
frequently prove useful to amateur me- 
chanics. It is remarkable for its sim- 
plicity and the common want it so readily 
and accurately supplies. The practical 
mechanic is frequently at his wit's end to 
find dimensions in peculiarly difficult 
places, which no tool he may possess is 
fitted to determine. 
The following illustration will serve to 
show how simple a thing it is to get the 
dimensions of any piece of work in what- 
ever shape it may be. The casting in this 
A NEW WAY TO MEASUEE. 
case being of spherical form, with flange, 
it would puzzle most mechanics without 
special tools to find its ■ thickness. The 
first thing usually resorted to would be to 
drill a hole at a designated point. The 
above wrinkle provides a readier method, 
and does away with the application of 
special tools. By simply applying a com- 
mon rule, as shown, and setting the caliper 
to some even inch on the rule, so that it 
SCIENTIST. 83 
may easily be removed, it will be seen that 
the difference between the even inch de- 
noted and the actual oi^ening of the 
caliper is the dimension required. 
Bleaching and Dyeing Bone and Ivory. 
IVOEY is so frequently used by the am- 
ateur workman, and enters into the 
formation of so many instruments, that a 
good method of bleaching it is of great 
value. 
M. Cloez being consulted by M. Gra- 
tiolet on the best way of removing the 
yellowish and fatty appearance of skele- 
tons, as well as their unpleasant odor, 
advised the use of the solvents for fatty 
bodies, and especially the oil of turpen- 
tine. He was surprised to see not merely 
that the cadaverous odor disappeared in 
a short time, but that the bones became of 
a dazzling whiteness. 
The same process applied to ivory gave 
a perfect bleaching. An exposure of three 
or four days to the sun in oil of turpentine 
is quite sufficient. An essential precaution 
is to support the objects to be bleached 
upon little supports of zinc, so that they 
may be raised a few millimetres above the 
bottom of the glass vessel in which they 
are placed. 
Oil of turpentine is, in fact, a very 
powerful oxidizing agent, and it acts by 
reason of this property; the product of 
the reaction forms an acid liquid, which 
spreads on the bottom of the vessel in a 
shallow layer, and if the objects to be 
bleached dip into this acid liquid they be- 
come attacked. 
The action of the oil is not only exerted 
on bone and ivory— it acts also upon 
woods and other bodies. Beech, maple, 
elm, yield excellent results, and cork is 
whitened very rapidly. Oil of turpentine 
is not the only one which possesses these 
properties; oil of citron and the other 
isomeric oils possess the same effect. 
Ivory is easily dyed in different colors, 
but in order that the dye may be fast, the 
articles to be dyed should be previously 
steeped from six to eight hours in vinegar, 
or better, in a solution of alum. They 
may then be dyed a fine red by a decoc- 
tion of Brazil wood ; yellow with saffron 
