THE ALUMNI JOURNAL. 



35 



nent picture. How it came about puzzled 

 him a great deal. In looking around the 

 closet where these pictures were exposed 

 — where these plates were stored — he 

 found that for some reason or other the 

 bottle of mercury had been broken, and 

 he tried almost every imaginable ma- 

 terial in the closet, and at last it struck 

 him it might be mercury. Well, he put 

 some mercury on the plate and he ruined 

 it. "Well, no," he says, "it is not mer- 

 cury but mercury in a very fine state. I 

 wonder if it is the Vapor of Mercury -?" 

 He tried it and found that it was. That 

 led to the development of the daguerreo- 

 type. Then all he did with a plate was 

 to put it into a vessel with a few drops of 

 mercury, and underneath a little spirit 

 lamp. Then he would put the plate in 

 and watch the heat (some now have a 

 thermometer) and he would just pick it up 

 every once in a while to see how it is 

 developing. That process gave to him 

 the first picture, the daguerreotype, and 

 those are to-day the handsomest pictures 

 ever made by photography. I have two 

 or three of them which are partly spoiled, 

 but to day they far surpass anything we 

 have ever since done in the science of 

 photograph}^. After the mercury pro- 

 cess, it was very easy to wash the plate 

 off. The object of the development was 

 this : that where the light had acted there 

 the mercury seemed to take hold and 

 bring out the picture. Where the light 

 had not acted you could dissolve the sil- 

 ver surface off with cyanide of potassium, 

 which was generally used. But, if you will 

 look at this old-fashioned daguerreotype, 

 you will see that you had to look at them 

 in a certain light; otherwise, you could 

 see nothing. 



Sometime afterwards a man named 

 Fitsherbert, a Frenchman, conceived the 

 idea of changing this peculiar picture in 

 silver plate into a gold picture. In other 

 words, he put into the plate a little chlo- 



ride of gold and produced a daguerreo- 

 type which can be seen pretty clearly by 

 looking squarely at it. 



The beginning of the daguerreotype 

 flourished only a short time. While Da- 

 guerre and others were working at the 

 daguerreotype, Fox Talbert, a rich Eng- 

 lishman, took up the subject from an- 

 other point of view. He conceived the 

 idea of making a negative. Of course, 

 every picture you took by Daguerre's 

 method you had to make a sitting for it. 

 Such are the pictures up in the School of 

 Mines of William Lloyd Garrison and 

 Daniel Webster. They had to sit right 

 down in front of the box, and copies 

 could not be had. That was the trouble 

 with the daguerreotype. You had one 

 picture for every sitting. To make the 

 difference between the positive and nega- 

 tive more clear, I have brought here to 

 show you to-night (producing them) 

 some positives and negatives printed on 

 the same piece of paper. When the 

 picture comes out of the camera and the 

 plate is developing (exhibiting it) that 

 is what it looks like — where the light 

 struck all the light parts of the picture 

 are black, and where the light did not 

 strike all the black parts of the picture 

 are white. If I take the same surface, 

 containing the bromide of silver, iodide 

 of silver or chloride of silver, and place 

 it underneath that and expose it to the 

 sunlight, where the light strikes through 

 it will produce black, just as in the 

 original object, and when I get through 

 I get the positive. So there is a neg- 

 ative and there is a positive from the 

 same picture. Now, that was Fox Tal- 

 bot's idea. He says " If I can do that, 

 I can make pictures ad libititm." With 

 this object in view he coated paper with 

 silver chloride. He exposed it then in the 

 camera, fixed it in a solution of salt — 

 common salt or iodide of potassium — and 

 when he got through the picture was a 



