The trouble with these paper pictures was that you could not eliminate the grain of the paper, and if you will examine these close enough you will see that they are blurred. This one printed from that particular negative is blurred--very much blurred. These sensitive silver compounds are so sensitive that the grain of the paper produces an impression. Now, in 1848, Niepse, a nephew of the first Niepse, thought it would be a good idea to use glass plates coated with albumen. He took chloride or iodide of silver, mixed it with white of egg, spread it on plates, heated the plates, which, of course, coagulated the albumen, and that fixed his film upon the glass plates. That was quite a step. Now, we had gotten rid of the paper. By the way, I made a little mistake there about the way he got the picture. He got the picture by putting salt in the albumen and then coagulating it, and then he dipped the plate into a solution of silver nitrate and in that way got the precipitate in the film itself. This was important but troublesome and not always successful. Now, a few years before another discovery was made. Remember that this was in 1848 that Niepse worked with the albumen process. In 1840, Schurben, a Swiss chemist, discovered gum cotton. This gum cotton is a nitrated compound of cotton, made by the action of concentrated sulphuric and nitric acids upon cotton. Sometime afterwards Maynard, a Yankee, in Boston, discovered that this gum cotton was soluble in alcohol, and ether, and then he found that by evaporating the substance he got the thin film of collodion. Scott Archer, an Englishman, conceived the idea of using this film as a vehicle for these particularly sensitive silver salts for photographing. His method was pretty much that which is followed to-day and that is still in use to quite a large extent. In this process we have this series of operations: First, the plate must be perfectly clean. That is essential. Any little spot upon it will form a nucleus which will spread over the surface of the plate. The plate is then coated with albumen and allowed to dry without heating. It is then flowed with this collodion, and in the collodion is put the chloride, iodide or bromide of silver, which you need. It is generally the chloride, iodide or bromide of silver. This collodion is afterwards dipped into a silver bath, and then we get the sensitized silver surface, very thin and perfectly transparent. It is then ready to go into the camera. It is put into the camera soaking wet with nitrate of silver. It is exposed and then developed with a solution of sulphate of iron with some acetic acid. After it is developed, the developer is washed off, fixed with hypophosphite of sodium, dried, varnished and we get the negative.