Daguerre delayed the publication of his process until a pension of six thousand francs per annum had been secured to himself, and four thousand francs per annum to M. Isidore Niépce for life, with a reversion of one-half to their widows. In the midst of political and social struggles France was proud of the glory of such a marvellous discovery, and liberally rewarded her fortunate sons of science with honourable distinction and substantial emolument. She was proud and generous to a chivalrous extent, for she pensioned her sons that she might have the "glory of endowing the world of science and of art with one of the most surprising discoveries" that had been made on her soil; and, because she considered that "the invention did not admit of being secured by patent;" but avarice and cupidity frustrated her noble and generous intentions in this country, and England alone was harassed with injunctions and prosecutions, while all the rest of the world participated in the pleasure and profits of the noble gift of France. In July, 1839, M. Daguerre divulged his secret at the request and expense of the French Government, and the process which bore his name was found to be totally different, both in manipulation and effect, from any sun-pictures that had been obtained in England. The Daguerreotype was a latent image produced by light on an iodised silver plate, and developed, or made visible, by the fumes of mercury; but the resultant picture was one of the most shimmering and vapoury imaginable, wanting in solidity, colour, and firmness. In fact, photography as introduced by M. Daguerre was in every sense a wonderfully shadowy and all but invisible thing, and not many removes from the dark ages of its creation. The process was extremely delicate and difficult, slow and tedious to manipulate, and too insensitive to be applied to portraiture with any prospect of success, from fifteen to twenty minutes' exposure in bright sunshine being necessary to obtain a picture. The mode of proceeding was as follows:--A copper plate with a coating of silver was carefully cleaned and polished on the silvered side, that was placed, silver side downwards, over a vessel containing iodine in crystals, until the silvered surface assumed a golden-yellow colour. The plate was then transferred to the camera-obscura, and submitted to the action of light. After the plate had received the requisite amount of exposure, it was placed over a box containing mercury, the fumes of which, on the application of a gentle heat, developed the latent image. The picture was then washed in salt and water, or a solution of hyposulphite of soda, to remove the iodide of silver, washed in clean water afterwards, and dried, and the Daguerreotype was finished according to Daguerre's first published process.