SCIENTIFIC AMERICAN SUPPLEMENT, No. 276. 4401 (the dead side) for the lamp to refiect on; place a sma�l bo,x or anythin&, handy under the aperturll, so as to b�w� It within an lUch of it; by varying the ligh� y?u . ca:1I SUlt lt to thick or thin negatives. I do not find It InJurlOus to the si"ht· but it would be advisable for any oue t,) wear specta c1�s �ith a blue or green tint, for without good eyesight the photographer is lost -P hotographie News. were of more importance than the obtaining

more »

... f good grada-pounds will, therefore, be contained likewise only in 2 vols. tion and half·tint? A thick, creamy film is certaiuly a of eitber of the above cblorides, and it is assumedbeautiflll tbing to look at, but worth little in general �ork; 5. Tba:t the nllm�er . of mole?1l1es represenr . ed b.y t�e mole· for as development cannot be witne8�ed as the film 18 not cular welgbt = 2 x IS m every lI]stanCt' contallled In 2 vols. tra�sparent there can be no certainty as ' to when the proper I This a�sumption is supported by the general fact thaI tbc density is �eached. This is most important, for if carried product ()f the combination of gaseous bodies is generally too far the rationale of alkaline development iR that half-= 2 vols.; it involves the final amI important couclusion- tones are lost by being developed up more or less to the 6. That combination of compounds results always in conhigh li not . re�ember havin� seen auywhere a description of anythtng slmllar, tbe folloWlllg may, perhaps, interest .y our readers. which is a comfort not to be despised; and, lastly, the half-It is erroneously stated* that one atom of bydrogen,of tints and gradation l}re not obliterated.-Harry Rogers, in chl?rine, etc. , occupies 1 vol.; tl:ue only is tbat, if the British Journal of Plwtography.