Messrs. Swift exhibited a microscope on their four-legged tripod model, but made of aluminium throughout, with the exception of the rack work, screws, and wearing surfaces, these latter being of steel, or faced with thin steel plates. All the fittings, as eyepieces, sub-stage condenser, etc., were also of aluminium, including the entire mount of the objective shown, which Messrs. Swift believed was one of the first so constructed. The President thought the use of aluminium for the objective mount was greatly to be commended, as it would be n great saving of strain on the fine adjustment, in some forms at least.
Karop believed that one drawback to the use of aluminium was that it was a very expensive metal to work—the screws and racks also had to be made of some harder metal, he thought this difficulty might be met to some extent by making an alloy of aluminium with some other metal which would give it greater hardness, while retaining some of the advantages of lightness.
Mr. M. Swift said this could no doubt be done, but as soon as they began to get harder alloys they got them heavier.
Mr. Michael said it was easy to make an alloy of aluminium, which was an exceedingly hard metal, but it was not exactly a tough metal, at least so he found some years ago when he was considering the possibility of making a microscope of this kind. He thought, however, that the great value of this light weight was where they wanted a travelling microscope—for it did not much matter in the case of one which was to be used at home; but if there were to be steel parts introduced, were there any means taken to prevent these from rusting?
Mr. M. Swift said the working parts were always lubricated with oil, and this was found sufficient to prevent rust. He might also say that when Mr. Michael approached them some years ago on this subject, the aluminium which they were then able to get was much more difficult to work than the kind they were able to obtain now.
The thanks of the meeting were voted to Mr. Swift for his exhibit.