Fig. 3 shows a spindle with a very long conical oil vessel, B, resting upon a disk, e", in cup, e', with a cover, e"'. The wharf, d, is here situated high up the spindle, has the same sleeve as in the preceding case, and runs round the bush, g, upon the ring, z. The friction plate resting upon the wharf is joined to the collar, a, running out into a cup shape, which is fixed to the spindle, which here has a hexagonal form. In this case the collar gives with the spindle, which latter has the necessary play in the long footstep; and as the collar and friction-plate are one, it is brought back to its normal place by centrifugal force.
A peculiar arrangement is shown in Fig. 4. Here the ring and traveler, f, are placed as usual, but the spindle carries at the same time an inverted flier, t. The spindle turns loosely in the footstep, e, the oil chamber being carried up to the middle of its height. The wharf is placed in the same position as in the previous case, having also a sleeve running in the oil chamber, c, upon a steel ring, z. The friction-plate a, on the top of the wharf carries the flier, and on its upper surface is in contact with the inverted cup, a, which is attached to the spindle by a pin or screw. In order to limit at will the lateral motion of the spindle there is attached to the latter, between the footstep and the collar, a split ring, i, which can be closed more or less by a small set screw. The spindle is thus only held in the perpendicular position by its own velocity, which will facilitate a high degree of speed, through the entire absence of all friction in the bearings, this vertical position being assisted by the friction motion whenever the spindle has been drawn on one side. Although the notion of mounting spindles so that they can yield in order to center themselves is not new, it is evident that considerable ingenuity has been brought to bear upon the arrangement of the spindles we have described, but we are not in a position to say to what extent practice has in this case coincided with theory.--Textile Manufacturer.
PHOTO-ENGRAVING ON ZINC OR COPPER.
By LEON VIDAL.
This process is similar in many respects to the one which was some time ago communicated to the Photographic Society of France by M. Stronbinsky, of St. Petersburg, but in a much improved and complete form. An account of it was given by M. Gobert, at the meeting of the same society, on the 2d December, 1882. The following are the details, as demonstrated by me at the meeting of the 9th of May last:
Sheets of zinc or of copper of a convenient size are carefully planished and polished with powdered pumice stone. The sensitive mixture is composed of:
The whites of four fresh eggs beaten
to a froth......................... 100 parts
Pure bichromate of ammonia......... 2.50 "
Water.............................. 50 "
After this mixture has been carefully filtered through a paper filter, a few drops of ammonia are added. It will keep good for some time if well corked and preserved from exposure to the light. Even two months after being prepared I have found it to be still good; but too large a quantity should not be prepared at a time, as it does not improve with keeping.