Rev. H. G. Your letter has been forwarded to A. F. B. (Diss).
S. Z. Z. S. We have a letter waiting for this Correspondent; how can we forward it?
C. E. F. Warm water and a few small shot will thoroughly cleanse the bottles in which collodion has been kept.
An Amateur Experimentalist. Formerly the pint used in the compounding of medicines, chemicals, &c. consisted of sixteen fluid ounces, weighing one pound Avoirdupois weight. Now the imperial pint of twenty ounces is in general use. The Troy and apothecaries' ounce are the same, and contain forty grains more than the Avoirdupois ounce. In making collodion, take any quantity of ether, and dissolve the gun cotton in it; if too thick, it may always be reduced by the addition of more ether. Uniodized collodion may be bought quite as cheap as it may be made; and it generally has the advantage of having been made in a large body, and allowed time to settle, whereby the clear portion only is more easily decanted off for sale.
Having active professional duties, it has been only at his leisure that Dr. Diamond has been enabled to give his attention to Photography, which has been the main cause of the delay complained of; but the delay will prove an advantage, for such important improvements are almost daily taking place in the art that works published a short time since are becoming comparatively useless.
Hugh Henderson. 1st, Black Japan varnish is very improper for your positive pictures; it often cracks, and is long in drying. Black lacquer varnish, procurable at Strong's, the varnish makers in Long Acre, is the best we have been able to procure. 2nd, The solution for development will keep any length of time; you may use it by dipping or otherwise.
W.C., who recommends the use of a plate glass bath enveloped in gutta percha, is informed that we have had such a bath in use for many months, and it answers our purpose exceedingly well.
Abraham. As we have often said before, we think that a good lens requires no "actinic" focus to find. In a properly constructed lens the chemical and visual foci are identical; and we would ourselves not be troubled with the use of one in which they differed. Our advertising columns will point out to you where such a lens man be procured. We believe, where there is a difference between the two foci, chemical and visual, that other distortions also take place, accounting for some of the unpleasant effects complained of in Photography.
A few complete sets of "Notes and Queries," Vols. i. to vii., price Three Guineas and a Half, may now be had; for which early application is desirable.
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