H. HENDERSON (Glasgow). _We consider glass baths are much superior to gutta percha in every respect. Many of the unpleasant markings in collodion pictures may have their origin in the gutta percha. This is frequently adulterated, and the nitrate acts upon the extraneous substances which are added to the gutta percha, either for adulteration, to give it firmness, or an agreeable colour. A glass bath is readily made, but the minute details of the mode we cannot enter into. Our Correspondent is referred to our numerous advertising friends, as the readiest way to supply his present want in this respect. "Jefferies' Marine Glue" can be procured at all times, the cost being about sixpence per pound. One part of marine glue, and two of best red sealing-wax, form a beautiful cement for glass baths. The marine glue, when used alone, becomes detached from the glass by the nitrate solution; and, without a substance to temper it, the sealing-wax is too brittle._ X. (Manchester). _When the blue spots occur of which our Correspondent complains, it is because there is at the time of operating very feeble actinic action in the light. If he were to rub one of these pictures when dry, he would find it almost entirely removable from the glass. The occasional want of brilliancy in all probability depends on the same cause. Proto-nitrate of iron, when prepared with the nitrate of baryta of commerce, instead of pure nitrate of baryta, will often have the same effect._ * * * * * Now ready, in one volume, price 21s., SOME ACCOUNT OF DOMESTIC ARCHITECTURE IN ENGLAND during the FOURTEENTH CENTURY, with Notices of Foreign Examples, and NUMEROUS ILLUSTRATIONS of existing Remains from ORIGINAL DRAWINGS, by the editor of the "Glossary of Architecture." Also, THE TWELFTH and THIRTEENTH CENTURIES, by the late MR. HUDSON TURNER. Uniform, price 21s. Oxford & London: JOHN HENRY PARKER. * * * * * BOOKS FROM DAWSON TURNER'S LIBRARY. CATALOGUES GRATIS and POST FREE (Ready on Monday).--W. S. LINCOLN'S Ninety-first Catalogue (for April) will entirely consist of Books purchased at the Sale of the Valuable and Important Library of DAWSON TURNER, Esq., F.R.S., of Yarmouth. A Copy will be sent Gratis and Post Free, Town or Country, to any Gentleman who forwards his Address to CHELTENHAM HOUSE, WESTMINSTER ROAD, LONDON. * * * * * 3 vols. 8vo. price 2l. 8s. A GLOSSARY OF TERMS USED IN GRECIAN, ROMAN, ITALIAN, AND GOTHIC ARCHITECTURE. The Fifth Edition enlarged, exemplified by 1700 Woodcuts. "In the Preparation of this the Fifth Edition of the Glossary of Architecture, no pains have been spared to render it worthy of the continued patronage which the work has received from its first publication.