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POPULAR SCIENCE REVIEW. 
is always a definite similarity. Old sub-angular flints and tools, 
again, have a well-defined lustre or patina due to alteration of 
the surface, and this peculiar appearance is difficult, if not im- 
possible, to produce. Given, therefore, a stone shaped by bold 
chipping into an axe-like shape, with a wavy edge, shining with 
a tint unlike that of a freshly-broken stone among the relics of 
a surface-find, and it may be classed undoubtedly as a human 
tool. 
But what, it is often asked, is the use of a study the materials 
for which are rare, the deductions from them so problematical ? 
Now nothing could be more injudicious than to attempt to gauge 
the value of any knowledge by the results of the work done in 
one generation. Human life is too short for men to do more 
than further little by little the work of the preceding time, 
regardless, as a rule, whether their contribution to knowledge is 
worth preserving or not. Posterity will be the best judge of 
that. The philosopher who first applied two different pieces of 
metal to the leg of a frog and noticed that the muscles moved, 
scarcely foresaw that from that insignificant experiment would 
come the science of electricity and the shilling telegraph. 
When James Watt, pressing the lid of his aunt’s teapot, found 
that steam had lifting power, he probably did not dream that 
from the development of the fact would come steam-ships that 
would move against wind and tide, and railways with engines 
that could travel at the rate of sixty miles an hour. 
The old alchemists who, in their search after an imaginary 
philosopher’s stone, discovered many a previously unknown 
chemical combination, many a hidden secret of nature’s labora- 
tory, did not imagine that the practical result of labour they 
then regarded as useless would be a better system of medicine, 
a more extended usefulness in the arts. 
They worked for their own time, satisfied to do the work that 
pleased them best well, and left to future generations to accept 
what was good and reject what was bad in it. So with this 
study, one yet in its infancy even now. The most interesting 
study of mankind is man. All history is useful as teaching us 
lessons of what has gone before. Here we have traces of very 
ancient history indeed. Weak as the traces are they tell some- 
thing of man’s early habits before written records took the place 
of stone. 
Then, again, even the value of a study should not always be 
measured even by its practical usefulness. In that charming 
book which all boys either have, or should have, read, 
44 Evenings at Home,” there is a story entitled 44 Eyes and no 
Eyes.” It tells how two lads went in different directions for a 
walk and one returned with body exercised, it is true, but with 
mind unrested by the only rest mind can have — change of 
