1108 Transactions of the American Institute. 



keep indefinitely. I have some now on hand, made nearly eight 

 months ago, which has undergone no perceptible change. I use hot 

 water, six ounces ; finely pulverized sugar of milk, quarter of an ' 

 ounce ; tannin, forty grains ; tincture of opium, one half drachm ; put 

 together in the order here given. The sugar of milk dissolves very 

 slowly, unless pulverized and placed in hot water. The addition of 

 the opium causes a precipitate in the solution, and it should stand at 

 least twenty or thirty minutes before it is filtered. I prefer sugar of 

 milk to any other saccharine substance, because, unlike all others, it 

 is not liable to alcoholic fermentation, which always precedes 

 putrescence or the generation of putric acid, in saccharine solutions. 

 With plates prepared by this preservative, I have made negatives in 

 •the month of June, using four and a half inch focus lenses and a- 

 quarter inch diaphragm, in five and six seconds, with the alkaline 

 developer, which was quite as quick as I could make them with wet 

 plates. I also prepared some plates with a modified coffee process, 

 the only material difference being the substitution of sugar of milk, 

 twenty grains to the ounce, for the loaf sugar usually prescribed. 

 This solution keeps, and can be used, for months without exhibiting 

 any symptoms of change. The sugar of milk forms a very hard and 

 dry varnish on the surface of the sensitized film ; and another ofiice 

 which it appears to perform, is to render the negative soft and 

 harmonious, preventing violent contrasts. That the sugar of milk 

 has this tendency, I proved by making some dry plates preserved 

 with sugar of milk alone. Coffee plates prepared by this formula 

 are very sensitive, but not quite as sensitive as those by the preceding 

 process ; they keep, however, equally well, and in this respect, as 

 also in the quality of the negative, are all that can be reasonably 

 desired. The process is simple and efficient. 



I have succeeded in perfecting a tea process which is reliable, and 

 in most respects, produces results similar to the coflee. I experi- 

 mented with several samples of Oolong tea, with difierent results in 

 almost every instance. I theit procured some Japanese tea, and the 

 plates resulting from its use were very fine. I have since experi- 

 mented with different samples, and the results have been uniformly the 

 same. I make a strong tea, using a large spoonful, which I put into 

 a bowl and pour on eight or ten ounces of boiling water, then cover it 

 over, and keep it hot for about an hour, then make it up to ten or 

 twelve ounces ; add, while hot, fifteen to twenty grains to the ounce 

 of finely pulverized sugar of milk, filter, and as soon as cool, it is 



