Note 4 — Chapter XIII · HEAT.

As in the case of many other inventions, so here the same idea was originated and put to practical use by more minds than one. George Stephenson, who from being a common engine-wright in a colliery rose step by step till he invented the locomotive, constructed a lamp which illustrated in another way the same principle as the lamp of Davy does—in other words, he invented another safety-lamp. But this does not in the least detract from the glory which the invention has given to the name of Davy, for each acted independently of the other. In Davy's case, it is to be remarked, there was a long course of scientific reasoning and investigation which led him at length to the invention, the record of which is exceedingly interesting. No invention or discovery is made without thought, though accident may suggest the thought; but here is an invention which, without any suggestion by accident, was evolved by laborious and long-continued thought, proceeding step by step to its conclusion.