These details may appeal trifling, and others may have more ingenious modes of accomplishing the object; but having used baths so constructed upwards of twelve months without leakage, I believe they will be found to be most economical, and far more to be relied on than gutta percha. A good bath so made should require about six ounces of solution of nitrate of silver to take a picture eight inches square. Your observations in a former Number, respecting the uncertainty of gutta percha, I have found to be perfectly true. Samples of gutta percha constantly vary; and one may contain impurities acted upon by the chemicals, which another does not. A small rim formed by sealing-wax dissolved in spirits of wine, and applied twice or thrice along the upper edge of the bath, is sufficient to protect the prepared glass from adhering to the front of the bath when in use. H. W. D. _Securing Calotype Negatives._--Will any of your correspondents be good enough to say what they consider the best method of securing a calotype paper negative for a few days or a week, in cases where it may be difficult, from lack of conveniences during that time, to use hyposulph., with its consequent washings, &c.? Some, I believe, recommend bromide of potassium; some, the iodide; others, common salt: but I should like to know which is considered the _best_; what strength, and how applied. Also, whether any subsequent treatment is necessary previous to the final application of the hypo. W. T. * * * * * Replies to Minor Queries. _Wood of the Cross_ (Vol. vii., pp. 177. 334.).--I find, in your 179th Number, p. 334., a communication on "The Wood of the Cross." Mention is made of the several kinds of wood of which the cross is said to have been made--elder, olive, &c. It is a somewhat curious coincidence, that yesterday I was with a farmer in his garden, and observing on several apple-trees some luxuriant mistletoe, I remarked that it was principally found on that tree, sometimes on the oak, but rarely on other trees. The farmer, after inquiring whether it could be propagated by cuttings, &c., asked if I had ever understood that our Saviour's cross was made of mistletoe? On replying in the negative, and remarking that it was altogether unsuitable for such a purpose, he rejoined, that, previously to that event, it was a large strong tree, but subsequently had been doomed to have only a parasitical (not that he used the term) existence. As CEYREP said "I never heard of our Lord's cross having been made of elder wood," so I would also add, I never heard before of its being made of mistletoe. Did any one else ever hear of this tradition? S. S. S. _Bishops' Lawn Sleeves_ (Vol. vi., p. 271.).--J. G. T. has inquired concerning the date and origin of the present robes of Anglican bishops. Mr. Trevor thus describes the bishop's dress in Convocation, which is the proper dress of the episcopate: