"But this image always appears simple and clear. In order to get the ideal solution into practice, there is required a struggle against matter, and the bringing to an issue is the most thankless part of the inventor's work.
"In order to give consistence and body to the idea caught sight of enthusiastically in an aureole, one must have patience, a perseverance through all trials. One must view on all sides the mechanical agencies that should serve to set the image together, until the latter has attained the simplicity that alone makes invention viable. In this work of bringing to a head, the same spirit of invention and imagination must be constantly drawn upon for the solution of all the details, and it is against this arduous requirement that the great majority of inventors rebel again and again.
"This is then, I believe, how one may in a general way understand the genesis of an invention. It follows from this that here, as almost everywhere, the imagination acts through association of ideas.
"Thanks to a profound acquaintance with known mechanical methods, the inventor succeeds, through association of ideas, in getting novel combinations producing new effects, towards the realization of which his mind has in advance been bent."
But for a slightly explored subject, the foregoing remarks are not enough. It is necessary to determine more precisely the general and special characters of this form of imagination.
I term general characters those that the mechanical imagination possesses in common with the best known, least questioned forms of the constructive imagination. In order to be convinced that, so far as concerns these characters it does not differ from the rest, let us take, for the sake of comparison, esthetic imagination, since it is agreed, rightly or wrongly, that this is the model _par excellence_. We shall see that the essential psychological conditions coincide in the two instances.
The mechanical imagination thus has like the other its ideal, i.e., a perfection conceived and put forward as capable, little by little, of being realized. The idea is at first hidden; it is, to use our correspondent's phrase, "the germ," the principle of unity, center of attraction, that suggests, excites, and groups appropriate associations of images, in which it is enwrapped and organized into a structure, an _ensemble_ of means converging toward a common end. It thus presupposes a dissociation of experience. The inventor undoes, decomposes, breaks up in thought, or makes of experience a tool, an instrument, a machine, an agency for building anew with the débris.