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544 THE PHOTOGRAPHIC NEWS. mond and pearl weights, including the carat; 7, Avoirdu pois weight; 8, Weights for hay and straw; 9, Wool weight, using, as factor’s, 2, 3, 7, 13, and their multiples ; 10, Coal weights, decimal numbers, 1, ’5, -2, -1, -05, ’025. Besides these may be added the weights of the French metrical system, the gramme, &c., which is constantly used in this country by scientific men. Weights of the same denomination, moreover, vary in different localities. Thus there are about ten different stones : a stone of wool at Darlington is 18 lb.; a stone of flax at Downpatrick is 24 lb. ; whilst a stone of flax at Belfast is both 163 lb. and 24} lb., having in one place two values. The hundred weight may mean 100 lb., 112 lb., or 120 lb.; and if we buy a pound of anything, we must enquire how many ounces go to the pound, and if it belongs to Dutch, Troy, or Avoirdupois weight. All these discrepancies, and numerous others which are of only local importance, might be borne; indeed, the very annoyance to which they gave rise amongst persons en gaged in scientific pursuits, analytical chemists, photo graphers, and others, was gradually introducing a system of recording weights and calculating proportions in grains only, according to the first system noticed in our above list. Thus the chemist has his set of weights from 1000 grains down to the smallest fraction decimally divided, and never dreams of stating quantities in ounces and drachms, but gives the number of grains only, when the gramme system is not employed. The grain being always the same in every system, and invariably constant in the midst of such confusion, has been a sort of harbour of refuge to fly to, when drachms and scruples, pennyweights and ounces, became too complicated ; and it has always been our endea vour, seeing the numerous evils arising from the employment of two drachms (one the sixteenth part of 437} grains, and the other the eighth part of 480 grains) and two ounces in the ordinary requirements of every day life, to induce photographers to write, calculate, and give formula) in grains only. Our readers will, therefore, be as gratified as we ourselves are, to hear that the fierce onslaught which the General Medical Council has recently made upon the existing grain has been withdrawn, owing, in great measure, to the opposition which the proposed innovation excited amongst scientific men. Our reader’s are, no doubt, aware of the nature of the attack just made upon the old es tablished grain weight. A New Pharmacopoeia for the entire Kingdom is at present under preparation by the General Medical Council; and this body, in order to suit some views which they had of simplifying the mental labours of apothecaries’ assistants, proposed to upset the last trace of order and safety in our weights and measures, and introduce a most inconsiderate, inconvenient, and even dangerous change. Their proposition was to substitute the Avoirdupois for the Troy pound, to retain the Avoirdupois ounce, and to divide this ounce into 480 parts, each to be called a grain, in order to preserve the numerical values of the subdivisions of the ounce into drachms and scruples. Now, the Avoirdupois ounce containing only 437’5 standard grains, its division into 480 new grains would make that weight just about Ath less than the standard grain, and the same, of course, with the scruple and drachm. The atten tion of the College of Physicians having been formally called to this proposed innovation, that learned and in fluential body immediately passed a resolution, to the effect that, however desirable it might be to substitute the Avoir dupois pound for the Troy pound, it was not desirable to introduce a new grain differing from the standard grain which has been so long in use, and is established by Act of Parliament. We feel sure that all our readers will gladly endorse this resolution. The advantages to be derived from the change are comparatively small and doubtful ; about the confusion and the danger which would ensue from it there can be no doubt. Some advocates, more as apology than defence, have urged that, after all, the sub traction of th from the weight of the grain is a matter of [November 14,1862. small importance in pharmacy ; that supposing a. medical man of the present generation to take the change into con sideration when writing a prescription—a rather extrava gant supposition—and the dispenser afterwards to compound the medicine by the old weights, the addition to the dose, even if one ingredient were strychnine, would be attended with no risk to the patient; and with stronger reason it might be considered, that a difference of Ath in the various formula) used in photography could cause no serious harm. We do not admit this ; but if it were true, it would by no means justify the alteration. If the old weights could be at once discarded all over the country, the case might be different; but, as a matter of course, all recipes written or printed before the introduction of the proposed innovation would have to be made according to the old weights, and for that reason, the manipulator must retain these weights in use along with the old ones, when endless confusion would be sure to ensue; or he would have to constantly occupy his mind with arithmetical problems which would never lead to a perfectly accurate result. But it would not be merely in reading or writing recipes that confusion would be created. The unfortunate photographer would be beset with perplexities on every side. At present, when a scrapie of anything is named, he is in doubt as to whether 20 grains or 18’229106 grains is meant; but hitherto, when expressed in grains, he has felt safe. Were there, however, to be two grains in the field, he would never know which was meant. A formula for any solution would vary in strength according to the grain the writer meant, or the druggist used to compound it ; and in reading any physiological work, he would always be in doubt which grain was meant. These and other objections have been urged so forcibly upon the Medical Council, and the absurdity of introducing three grave difficulties for the purpose of removing one trifling inconvenience, have been so strongly laid before them, that at the last moment they have succumbed to common sense, and resolved not to interfere with the grain weight. They have determined, however, to retain the Avoirdupois pound, as proposed, against which no objection can be made, and also the Avoirdupois ounce, but discon tinue the use of the drachm and scruple. As the values of these latter weights are not affected, they will, of course, be used as heretofore, but now as merely denominational weights. This is, perhaps, the most sensible resolution the Council could come to; and with this arrangement, no practical difficulties need occur. A specimen of glass has been forwarded to us from Farringdon Lane, for examination in the spectroscope. To an ordinary observer, this seems of very excellent quality, being of a full deep brown ; and when compared side by side with a piece of good adiactinic orange glass, it still seems as if it might be trusted. It is darker than the orange glass, and of a browner tone. In the spectroscope, however, it is seen to be inferior. Rays, which the silver coloured orange glass would stop back, are freely trans mitted by it; and it is apparent that a photographic laboratory lighted through glass of this quality would bo inapplicable for delicate photographic purposes. ON DEVELOPING ROOMS. BY SAMUEL FRY. Why developing rooms should be called dark rooms seems difficult to decide, if we examine carefully into the charac teristics desirable for the convenient and facile development of pictures. That in nine cases out of ten they are dark rooms, none can deny, being generally miserable dark cells, in which the unaccustomed eye can perceive nothing but a faint dismal glimmer of yellow, until some minutes have elapsed. The primary cause of this wretchedness has been the iterated and reiterated counsel of certain photographic pundits. For example, Mr. Thomas says :—“ Use as 11 1 light as possible in the dark room and in going throng