I hope this little experiment will be useful to others, as a saving of 15 per cent. on the iodide of potassium is gained. As a large body of precipitated iodide of silver can be more completely drained than a smaller quantity, in practice it will be found that small precipitates require a few grains more than I have stated: thus, throw on the precipitate of iodide of silver (got from 150 grains of nitrate), drained dry, 960 grains of iodide of potassium; solution rapidly ensues, which, being made up to six ounces, the whole remains perfectly clear; whereas the iodide of silver thrown down from 50 grains of nitrate, similarly treated with 320 grains of iodide of potassium, and made up to two ounces (the proportional quantities), will probably require 10 or 15 grains more of iodide to effect perfect solution, the reason being that it contained a greater quantity of water _pro rata_ than the first. The following table, showing the exact quantities of iodide of potassium required to decompose 50, 100, and 150 grains of nitrate of silver, the resulting weight of iodide of silver, and the weight of iodide of potassium to make a clear solution up to 2, 4, and 6 ounces, will often be found useful: _Grs._ _Grs._ _Grs._ Nitrate of silver 50 100 150 Iodide of potassium 48.83 97.66 146.49 Iodide of silver 68.82 137.64 206.46 Iodide of potassium 320 640 960 Water up to 2 oz. 4 oz. 6 oz. T. L. MANSELL, A.B., M.D. Guernsey. _Mounting Photographs_ (Vol. ix., p. 282.).--J. L. S. will find the "Indian-rubber glue," which is sold in tin cases, the simplest and cleanest substance for mounting positives; it also possesses the advantage of being free from the attacks of insects. SELEUCUS. * * * * * Replies to Minor Queries. _Books on Bells_ (Vol. ix., p. 240.).--Add to MR. ELLACOMBE'S curious list of books on bells the following: "Duo Vota consultiva, unum de Campanis, alterum de Coemeteriis. In quibus de utriusque antiquitate, {311} consecratione, usu et effectibus plene agitur, pluraque scitu dignissima ad propositi casus, aliorumque in praxi, hac de re occurrentium decisionem, non injucunde adducuntur. Auctore D. Augustino Barbosa, Protonotario Apostolico, Eminentissimorum DD. Cardinalium Sacrae Congregationis Indicis Consultore, Abbate de Mentrestido, ac insignis Ecclesiae Vimarensis Thesaurario majore." [4to., no place nor date.]