A.E.B.--Extract of witch-hazel is made by distilling the leaves of that shrub, the scientific name of which is _Hamamelis virginica_. To do this, it will be necessary to secure apparatus especially adapted to the purpose. CARRIE N.--Polish the horns according to the directions given in Vol. 5, No. 43. They are very ornamental, but there is no great demand for them. You might be able to dispose of a pair or two among your friends. J.N.D.--Stamp dealers usually begin as collectors, and thus gain an intimate knowledge of the various issues, colors, varieties and prices of all the stamps issued. Numerous illustrated catalogues are issued by the principal dealers in this country and Europe. J.H.S.--1. When recharging a battery it is only necessary to remove any parts that may have decomposed and then add water. 2. The outfit requisite for producing the electric light described in Nos. 1 and 2 of the last volume will cost two or three dollars. OLD SUBSCRIBER.--Narrow shoulders may be strengthened and straightened by judicious exercise, and by walking and sitting erect, throwing them well back and never allowing them to droop. It is very doubtful, however, if their breadth can be increased to any appreciable degree. H.B.--Vols. 1, 2, 3 and 4 of this paper cannot be furnished complete either bound or unbound, but from 6 to 12, inclusive, they can be supplied in either shape. A very limited number of bound copies of the fifth volume remain to be sold at the usual rate of $4 each, but in its unbound form it is incomplete, one number being out of print. E.F.W.--White ink is made by mixing flake white with gum arabic and water. It should be sufficiently fluid to flow easily from the pen. Another mixture, erroneously called white ink, but which is in reality an etching fluid, and can only be used on colored paper, is made by adding 1 part of muriatic acid to 20 parts of starch water. A steel pen must be used. A.G.D.--1. There is but one way to improve the memory, and that is to concentrate the mind upon but one subject at a time, never allowing it to wander off to some other idea. At first, this is a difficult matter, but in a comparatively short time the mind can be brought under control, and the memory will, in many instances, become far more retentive than ever before. 2. The growth of hair on the face cannot be checked, but can be controlled by the regular use of a razor.