C. M. M. (Abbey Road). _Your question as to the spots has been carefully answered in a late Number. The film which you notice on the surface of your nit. silver bath depends upon the remaining portion of ether in the collodion being liberated, which, not being very soluble in water, causes the greasy appearance. It soon evaporates, and is of no consequence._ T. COOK _is thanked for his offer of a cheap and easy method of obtaining pictures for the stereoscope. We shall be glad to receive it._ DR. DIAMOND'S PHOTOGRAPHIC NOTES.--_We share in the desire expressed by_ W. C., J. M. S., _and many other Correspondents, for the speedy publication of this volume. But we believe the delay is not to be regretted. It is a very easy matter to write a book upon Photography; but it requires no small labour, and great consideration, to produce such a volume as_ DR. DIAMOND _proposes, in which it is his desire to explain everything so clearly, that a person living in a remote part of the country, or in the colonies, may, from his directions, make a good photograph._ _Errata._--P. 25., last line, read "camp_u_s" for "camp_re_s;" p. 26., fourth line, read "iar_o_" for "iar_s_;" p. 36., 2nd col. line 18., read "regularity" for "irregularity." _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._ "NOTES AND QUERIES" _is published at noon on Friday, so that the Country Booksellers may receive Copies in that night's parcels, and deliver them to their Subscribers on the Saturday._ * * * * * GILBERT J. FRENCH, BOLTON, LANCASHIRE, RESPECTFULLY informs the Clergy, Architects, and Churchwardens, that he replies immediately to all applications by letter, for information respecting his Manufactures in CHURCH FURNITURE, ROBES, COMMUNION LINEN, &c., &c., supplying full information as to Prices, together with Sketches, Estimates, Patterns of Material, &c., &c. Having declined appointing Agents, MR. FRENCH invites direct communications by Post, as the most economical and satisfactory arrangement. PARCELS delivered Free by Railway. * * * * * BENNETT'S MODEL WATCH, as shown at the GREAT EXHIBITION. No. 1. Class X., in Gold and Silver Cases, in five qualities, and adapted to all Climates, may now be had at the MANUFACTORY, 65. CHEAPSIDE. Superior Gold London-made Patent Levers, 17, 15, and 12 guineas. Ditto, in Silver Cases, 8, 6, and 4 guineas. First-rate Geneva Levers, in Gold Cases, 12, 10, and 8 guineas. Ditto, in Silver Cases, 8, 6, and 5 guineas. Superior Lever, with Chronometer Balance, Gold, 27, 23, and 19 guineas. Bennett's Pocket Chronometer, Gold, 50 guineas; Silver, 40 guineas. Every Watch skilfully examined, timed, and its performance guaranteed. Barometers, 2l., 3l., and 4l. Thermometers from 1s. each.