78 Practical Hints. 
to cover the top of one finger with the chamois and rub the nega- 
tive with a circular motion, changing the part of the chamois as it 
becomes black, and taking care to keep it well wet with the spirit. 
When portions of a negative are found to be over-intense, they 
can be reduced by the same method.” 
Slow v. Quick Plates.—A writer in the American Annual says: 
—T think it is folly to use quick-plates where it is possible to 
employ slow ones. Slow-plates generally contain more silver than 
quick ones, and therefore develop easier and quicker and secure 
more intensity. One or two seconds are not much in a lifetime, 
and a perfect negative is a very satisfactory thing. Not that 
perfect negatives cannot be obtained from quick-plates, but I 
contend that at least 75 per cent. more of perfect ones can be 
realised from the use of moderately slow-plates.” 
Practical Hints. 
Putting Screws into Plaster Walls.—It often becomes desir- 
able to insert screws into plaster walls without attaching them to 
any woodwork, but when we turn them in the plaster gives way, 
and our effort is vain. And yet a screw may be inserted in 
plaster so as to hold light pictures, etc., very firmly. The best 
plan is to enlarge the hole to about twice the diameter of the 
screw, fill it with plaster of Paris, such as is used for fastening the 
tops of lamps, etc., and bed the screw in the soft plaster. | When 
the plaster has set, the screw will be held very strongly. 
Gilding Ivory.—Immerse it in a solution of nitro-muriate of 
gold, and then expose it to hydrogen gas while damp. Wash it 
afterwards in water. 
Polishing Oak Furniture.—A bright polish may be attained 
by mixing six ounces of raw Jinseed oil with half the quantity of 
vinegar, to which, after being well mixed, three ounces of spirit 
and half-an-ounce of antimony is added. 
Coating to Imitate Amber.—A composition for the coating of 
wood or metals to imitate the finest amber, with brilliantly illumi- 
nated and iridescent reflecting surfaces, and in almost every 
shade, from the deepest yellow up to the deepest wine colour, is 
made from the nacreous portion of ordinary shells. The pow- 
dered material is first dried in an oven by heated air or gas, and 
immediately after subjected to the vapour of halogen, either in an 
oven or iron, glass, or porcelain vase, or a small muffler, to which 
heat is meanwhile applied, this heat vapourising the impregnating 
halogen elements applied, such as iodine, bromine, fluorine, 
