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56 MCINTOSH BATT ERY AND OPTICAL CO., CHICAGO, ILL., B. S. A. combinations will sometimes be brought in contact, and the flint glass, which is very thin in the center, will be broken. The screw thread of the cells is very delicate. Yet some persons, after failing to catch it, apply force enough to break it. Such carelessness passes compre- hension. “A large angle oil-immersion lens gets out of order easily. If you find the definition of such objective to have lost its sharpness, you may know that the front lens is out of center. It has come in contact with the slide. A very slight pressure is sufficient to work the mis- chief. This susceptibility to injury is unavoidable, as every optician will tell you. It is incident to the requirements of high angle con- struction. A few days ago an objective was sent to me with the request that the front lens should be reset. It had in some way been forced out of its place. I reset it as well as I could. But that objective, even if it had been repaired by its makers, the Messrs. Powell and Lealand, can never be what it was before the injury. The only way of repairing it was by inserting a ring of cement, which, projecting slightly through the shoulder, necessarily cut down the angle. A heavy shoulder means, of course, a low angular aperture. A novel method of using an immersion lens came under my notice recently. A water-immersion objective had been ordered. It was made and sent, but it did not give satisfaction. I inquired by letter, ‘ I n w hat way do you proceed to work with it ? ’ ‘ I fill it with dis- tilled water, and then screw it to the instrument,’ was the reply. An objective is sometimes almost ruined through sheer carelessness. I made a costly lens for a New York optician. He tossed it several times in his hand, and finally dropped it upon the floor. ‘Oh,’ he said, • that will not harm it 1 ’ I looked at it, and found the front combination tilted at an angle of about 45 °. This act of carelessness cost that optician twenty-five dollars. I have here the back setting of a inch lens which was made by me several years ago. The purchaser of the lens had screwed it so tightly to his microscope that he could not, with his hand, unscrew it. So he used a pair of heavy gasfitter’s pliers, and succeeded in pulling the tube of the fine adjustment out of the body of the instru- ment. This rude handling damaged the microscope to the amount of forty-five dollars. Quite recently the owner of an instrument which cost three hundred and fifty dollars told me that he had a wonderfully clever son. ‘ Why,’ he exclaimed, ‘ he has, with a screw driver, taken the microscope all apart! He is unable, however, to put it together again. This outrage illustrates the incapacity of some people, old as well as young, to appreciate the products of fine workmanship. I do not favor the nose piece, if you must have one, choose one that is of