The Optical Magic Lantern Journal (February 1893)

40 The Optical Magic Lantern Jou ral and Photographic Enlarger. ‘lantern, or meddling with the jet in any way. Other | will suffice. condensing lenses of different focus, can be instantly substituted to suit any change in the focus of the objective (as is shown in my paper refered to), or when the vertical attachment is to be applied, all that is necessary, is, to remove the back lens of the condenser, and apply the vertical attachment, the mirror of whichwill receive the practically parallel beam of lightemerging from the middle lens, and reflect it upwards to the back lens, which is now placed in its position on the vertical attachment, and thus the rays are condensed in a vertical direction by the same lenses asused in ordinary projection; and the change from one direction to the other, takes less time to perform, thanit does to read my description, so, what Mr. Fletcher means by ‘ the necessity for shifting the lime dangerously near to the condenser, and dispensing also with an extra condenser and consequent loss of light,*’ is best known to himself. It so happens that I gave a lecture, and a number of highly successful physical demonstrations in which the vertical attachment and triple condenser were used, just about the time you were in press with the January number. W. I. CHADWICK. The lecture refered to came after we had gone to press last month, but will be found on page 35 of this number. iD. CONVEYANCE OF COMPRESSED GAS CYLINDERS. {Lo the Editor.; Siurz,—Owing to the revised railway rates, the charges for tne conveyance of steel cylinders is particularly heavy by goods train, viz: a minimum of 5/for conveyauce, and 5/delivery. Protests have been made respecting , this, and the matter will no doubt be reconsidered by the railway directors, and brought down to the reasonable amount it was originally, or something nearit. Pending this change, all ianternists and users of compressed gas, are advised to send the cylinders by passenger train, for it is possible thus to send 200 miles including delivery for 3/3, as against 10/by. goods train.— Yours truly, J.H. STEWARD, 406, Strand, W.C. SITUATION IN THE UNITED STATES. To the Lditor. Six, —Ina recent copy of your journal, I observe among the alvertisements that a lantern operator has been advertising that he is desirous of treating with an American tirm, respecting obtaining a berth in this country. The advertiser is evidently unaware that it is against our law for a firm here, to engage labour of any description abroad, and so well is this law known here by both man and boy, that I should be very much surprised if he got a single reply. We employers have a sharp eye on matters of this kind, ana should anyone come ‘‘ across the pond”’ withan engagement, he would speedily find that the law would take cognisance of his arrival ; but if the advertiser were to come here and then look out for and obtain a situation. all well and good.—Yours obediently, A LANTERN OPERATOR. Chicago, Ill., U.S.A. —=$0: = Notes and Queries. L. J. Kay.—1, You can average the lime-light at 450 candle power, but the electric can run into figures that would seern fabulous. 2, The relative cost would be five orsix times. 3, It depends upon the candle power you wish to produce. 4, The storage battery. HW". Is. Holloway.—No matter whether the lens be a single or a double combination, the table of distances It is the focus only of the lens that has to be considered. If you wish to ascertain the focus of the double combination, allow the image of a distant object to fall on, say a sheet of paper fastened on the wall opposite a window, and when the object is sharply depicted, measure the distance between the paper and half way between the combination of the lens, this distance will be the focus. Novice.—1, We do not understand your difficulty in connection with vertical attachment. See the last few numbers of this journal, or we shall be pleased to answer definite questions. 2, Remove the objective and bring the light closer to the condenser. : J. C.—You will find the blow-through jet the best to employ until you have had some experience. J. R. writes: I have an elaborate mechanical slide that is broken, and I have had it at a watchmaker’s for repairs, but it does not work properly. Where can I have it seen to? <Answer.—We believe that Messrs. Wilkinson of Sunderland make it a speciality of repairing such slides. F.S. Sharman.—We called upon the firm, and doubtless. yon will have received your goods long before you see this. W’. Wans.—You will find more hints and information respecting lantern matters, in our back numbers, than in any book published. BP. Brewis.—We did not publish the January Journal on Sunday, although the date January Ist. fell on that day, but on the day previous. Mr. Stevenson recommended blowing through the tubes, before being used a second time in connection with a saturator, as he invariably finds that unless he does so, he has pops and bangs when lighting up. IW. Bird.—The address you require is Gilmer Bros., Manchester Buildinys, Cannon Street, Birmingham. a. ZL. Salter.—Replied by post. WW. Brown.—The condenser mentioned is good. The gas making apparatus mentioned in last Journal costs about £20, and can be obtained from the M’Intosh, Optica! Co., Wabash Avenue, Chicago, U.S.A. A. Lawson (New Zealand).—1, Use a jet with a smaller bore. 2, Write to Mr. W. Lawson, Rectory View, Newton-le Willow for particulars, or see page 53 of this Journal, for May 1892. We are pleased to hear that yon and your friends in New Zealand look upon this journal as a ‘‘marvellous pennyworth.” J. Clegg.—Heat applied to the saturator will make a great difference. The pattern you describe is not new, but one of the oldest, you could not expect a proper light with the jet mentioned, use a mixed jet with a medium sized nipple, and let us know how you get on. We have, after using the saturator, put out the light with no more noise than would be caused by a tap of a pencil ona table. You ask if an accident has ever occurred with a saturator ; yes. and so have steam boilers exploded under certain conditions, or when manipulated by one not conversant with them. L. L. G.—Legally you are not allowed to make such slides at all, it is often done for one’s private use, but you must not sell them, unless permission is obtained. One in Doubt.—1. Query came too late for us to ascertain. You can perhaps obtain the information you require from Brin’s Oxygen Co., Horseferry Road, Westminster, London. 2. No danger, fitting the tube as you suggest ; but the cylinders should be painted different colours. Prof. De Frere.—1. The general outlet is larger than the oxygen one, subsequently the gas could not mix in the manner you fear and get to the main. 2. If the outer cap or cone is adjustable, screw it a little further on, as the oxygen tube may be rather too far back. G. W. Smith.—Thanks. We have heard from Mr. G. and intend to write to you shortly upon the subject.