Sometimes this difference, though it seems to be small, is a mighty one when it comes to producing results as for instance when Elias Howe used a needle with the eye near its point instead of in its head and so made the sewing machine a commercial success. And yet a patent examiner of to-day would not be likely to see any difference in a needle with an eye in its head and one with an eye near its point, that is, if he had never seen either one before.
If you have made a machine to do a certain thing and you find that another machine has been invented that does the same thing and in the same way you may be able to change the mechanical movements, or electrical devices, until you are able to get the same or a better result by other and better means. It is all very easy to tell you to do this but in practice it is often a mighty hard thing to accomplish.
The Bell telephone is an example of such difficulties, for while both transmitters and receivers can be made which work on principles quite different from those now in use the results are not nearly as good and hence the inventions have no practical value.
When Others Are Exactly Like Yours.—But when you find that your great idea has been thought of and worked out and patented by some other inventor ahead of you and that both the cause and effect which you and he arrived at are the same, then the best thing to do is to drop it like a hot potato and invent something else.
Note.—The Patent Office publishes a Manual of Classification, price $1, which lists all of the sub-divisions of each class. Take as an illustration Explosives, which is Class 53. This is subdivided into six such classes, namely: (1) Blasting Powder; (2) Fulminates; (3) Nitro Compounds; (4) Gun Powder; (5) Matches; (6) Pyrotechnic Compounds.
CHAPTER IV
HOW TO EXPERIMENT
The kind of experimenting you will do will, of course, depend altogether on the nature of the invention on which you are working.
But, as good fortune would have it if you are not mechanically inclined you are not apt to hit upon a mechanical invention. And if you know nothing of electricity, you are not likely to think out an improved electrical device.