The sun was now fairly harnessed in the service of man in the new great art of Photography. Natural philosophers, chemists, inventors, mechanics, all now pressed forward, and still press forward to improve the art, to establish new growths from the old art, and extend its domains. Those domains have the generic term of _Photo-Processes_. Daguerreotypy, while the father of them all, is now hardly practised as Daguerre practised it, and has become a small subordinate sub-division of the great class. Yet more faithful likenesses are not yet produced than by this now old process. Among the children of the Photo-Process family are the _Calotype_, _Ambrotype_, _Ferreotype_, _Collodion_ and _Silver Printing_, _Carbon Printing_, _Heliotype_, _Heliogravure_, _Photoengraving_ (relief intaglio-Woodburytype), _Photolithography_; _Alberttype_; _Photozincograph_, _Photogelatine-printing_; _Photomicrography_ (to depict microscopic objects), _Kinetographs_, and _Photosculpture_. A world of mechanical contrivances have been invented:--_Octnometers_, _Baths_, _Burnishing tools_, _Cameras and Camera stands_, _Magazine and Roll holders_; _Dark rooms_ and _Focussing devices_, _Heaters_ and _Driers_; _Exposure Meters_, etc. etc. The _Kinetograph_, for taking a series of pictures of rapidly moving objects, and by which the living object, person or persons, are made to appear moving before us as they moved when the picture was taken, is a marvellous invention; and yet simple when the process is understood. Photography and printing have combined to revolutionise the art of illustration. Exact copies of an original, whether of a painting or a photograph, are now produced on paper with all the original shades and colours. The long-sought-for problem of photographing in colours has in a measure been solved. The “three _colour processes_” is the name given to the new offspring of the inventors which reproduces by the camera the natural colours of objects. The scientists Maxwell Young and Helmholtz established the theory that the three colours, red, green, and blue, were the primary colours, and from a mixture of these, secondary colours are produced. Henry Collen in 1865 laid down the lines on which the practical reduction should take place; and within the last decade F. E. Ives of Philadelphia has invented the _Photochromoscope_ for producing pictures in their natural colours. The process consists in blending in one picture the separate photographic views taken on separate negative plates, each sensitised to receive one of the primary colours, which are then exposed and blended simultaneously in a triple camera. Plates and films and many other articles and processes have helped to establish the Art of Photography on its new basis.