Prepare a sufficient quantity of this solution, and lay the sheet upon it in the same manner as before. Three minutes' contact will be sufficient with the thin negative paper, but if the Canson positive paper is used, lour or five minutes must be allowed for the decomposition. The papers are raised from this solution by a pair of bone forceps or common tweezers tipped with sealing-wax; or a pin may be used to lift up the corner, which is then taken by the finger and thumb and allowed to drain a little before again putting in the pin, otherwise a white mark will be produced upon the paper, from decomposition of the nitrate of silver. When the sheet is hung up, a small strip of blotting-paper suspended from the lower edge of the paper will serve to drain off the last drop of liquid. The solution of nitrate of silver becomes after a time discolored by the albumen, but may be used for sensitizing until it is nearly black. The color can be removed by animal charcoal,[M] but a better plan is to use the "kaolin" or pure white china clay. The writer has also tried the common "pipe-clay," which answered perfectly, but appeared to injure the sensitiveness of paper subsequently floated upon the bath (?). [Footnote M: Common animal charcoal contains carbonate and phosphate of lime the former of which renders the nitrate of silver _alkaline_; purified animal charcoal is usually acid from hydrochloric acid.] Sensitive albumenized paper, prepared as above, will usually keep for several days, if protected from the light, but afterwards turns yellow from partial decomposition. =Comparison of British and French Weights and Measures.= [Sidenote: WEIGHTS AND MEASURES.] WEIGHTS. Grain, Apothecaries' = 0·0648 grammes, French. Ounce " = 31·102 " " Avoirdupois = 28·346 " Drachm, Apothecaries' = 3·888 " ---- Gramme = 15·4310 grains, Apoth. Decigramme = 1·5434 " " Centigramme = 0·1543 " " ---- MEASURES OF CAPACITY. _Cubic Inches._ _Fluid Ounces._ Litre = 61·028 = 35·79 Decilitre = 6·02 = 3·57 Centilitre = 0·610 = 0·35 Millilitre = 0·061 = 0·03 ---- _Lb._ _Oz._ Killogramme = 2 3-1/4 Avoirdupois. ---- MEASURES OF LENGTH. Metre = 39·37 inches. Decimetre = 3·93 " Centimetre = 0·39 " Millimetre = 0·03 " ----