2 THE YOUNG 
his discoveries in regard to the colors of 
very thin films beyond the first steps, it 
taxed the utmost skill of the London op- 
ticians to supply him with lenses sufficiently 
accurate for his purpose. Franklin deter- 
mined by means of a kite the fact that light- 
ning and electricity are the same, but to 
investigate the laws of electricity requires 
apparatus of extreme delicacy and accuracy. 
Galileo discovered the moons of Jupiter 
with a telescope no better than that 
which any smart boy might construct for 
himself — lenses and all ; to discover the 
moons of Mars demanded the aid of a tele- 
scope which it required a master hand to 
produce. 
We hope our young frieijds will ponder 
these facts, and not be discouraged because 
they fail to accomplish, with inferior ap- 
paratus and tools, things which can be done 
only with the very best appliances. Neither 
should they be discouraged because they do 
not at first succeed in using their tools with 
the ease and skill which older hands have 
acquired. It is wonderful how far the skill 
which comes of long practice will carry one. 
And although good workmen generally 
have good tools, yet how often do we see an 
experienced hand accomplishing wonders 
with very inferior means? It is rare that 
a person of moderate experience can per- 
form an experiment successfully at the first 
trial. 
On the other hand, those who are com- 
pelled, by choice or necessity, to use niake 
shift apparatus, should feel diffident in re- 
gard to the importance and truth of any 
discoveries that they may make until these 
discoveries have been confirmed by more 
careful investigation, undertaken with more 
perfect appliances. In this connection it 
will be well to bear in mind the saying of a 
noted scientist, who, after listening to the 
praises of a young man who was said 
to have made some very wonderful dis- 
coveries with very inferior apparatus, ex- 
claimed: "Sir, it was not in spite of the 
badness of his apparatus that he made 
these supposed discoveries, but in conse- 
quence of it." 
SCIENTIST. 
General Rules to be Observed in Using 
Cements. 
OO much has been written concerning 
^ different cements, that our periodicals 
are full of recipes on this subject. But it 
will be found that the information given is 
rather in regard to the materials used in 
compounding these cements than in regard 
to the manner of using them, while it is un- 
questionably true that quite as much de- 
pends upon the manner in which a cement 
is applied, as upon the cement itself. The 
best cement that ever was compounded 
would prove entirely worthless if impro- 
perly applied. We have hundreds of recipes 
for glues, pastes and cements of different 
kinds, and yet the public is constantly on j 
the qui vive for new ones, and no more ac- j 
ceptable recipe can be sent to our popular 
scientific and technical journals than one 
for a new cement. Now, the truth is, that 
we have cements which answer every rea- 
sonable demand, when they are properly 
prepared and properly used. Good com- ! 
mon glue will unite two pieces of wood so ' 
firmly that the fibres will part from each 
other rather than from the cementing ma- 
terial; two pieces of glass can be so joined 
that they will part anywhere rather than on 
the line of union; glass can be united to 
metal, metal to metal, stone to stone, and 
all so strongly that the joint will certainly 
not be the weakest part of the resulting 
mass. What are the rules to be observed 
in efi'ecting this ? 
The first point that demands attention is 
to bring the cement itself into intimate con- 
tact with the surface to be united. Thus 
when glue is employed the surface should 
be made so warm that the melted glue will 
not be chilled before it has time to effect a 
thorough adhesion. The same is more 
eminently true in regard to cements that are 
used in a fused state, such as mixtures of 
resin, shellac and similar materials. These 
matters will not . adhere to any substance 
unless the latter has been heated to nearly 
or quite the fusing point of the cement 
used. This fact was quite familiar to those 
