November 6, 1891.] 



SCIENCE. 



255 



intermediate pair 6.7 and 6.1. And these are not isolated 

 facts. Comparisons of the same kind, and leading to identi- 

 cal conclusions, were made by Professor Eastman at Wash- 

 ington in 1889 (Phil. Society Bulletin, vol. xi., p. 143; Pro- 

 ceedings Amer. Association, 1889, p. 71). 



What meaning can we attribute to them ? Uncritically 

 considered, they seem to assert two things, one reasonable, 

 the other palpably absurd. The first — that the average 

 angular velocity of the stars varies inversely with their dis- 

 tance from ourselves — few will be disposed to doubt; the 

 second — that their average apparent lustre has nothing to 

 do with greater or less remoteness — few 7/ill be disposed to 

 admit. But, in order to interpret truly, well-ascertained if 

 unexpected relationships, we must remember that the sensi- 

 bly moving stars used to determine the solar translation are 

 chosen from a multitude sensibly fixed ; and that the propor- 

 tion of stationary to travelling stars rises rapidly with de- 

 scent down the scale of magnitude. Hence a mean struck 

 in disregard of the zeros is totally mi.sleading; while the 

 account is no sooner made exhaustive than its anomalous 

 character becomes largely modified. Yet it does not wholly 

 disappear. There is some warrant for it in nature. And 

 its warrant may perhaps consist in a preponderance, among 

 suns endowed with high physical speed, of small, or slightly 

 luminous, over powerfully radiative bodies. Why this 

 should be so, it would be futile, even by conjecture, to attempt 

 to explain. 



AN INGENIOUS FORGING PRESS. 



Me W. D. Allen, in a paper read at the autumn meeting 

 of the Iron and Steel Institute, London, in October (Nature, 

 Oct. 15), described a forging press, which, although it has 

 been at work for some years at the Bessemer Works in 

 Sheffield, is so ingenious, and so new to most people, that it 

 is worthy of description. The press has the appearance of 

 a steam hammer, and, indeed, there is a steam cylinder at 

 the top, just as in a hammer. The use of the ster.m, how- 

 ever, is only to raise the " tup " when the hydraulic pressure 

 is released. The press consists of an anvil block below and 

 a ram above, the work being in a vertical direction. The 

 ram works in a hydraulic cylinder, and is carried through 

 the top end of the latter in the shape of a stout shaft or 

 shank, which may be described as a tail-rod to the ram. At- 

 tached to this is the piston rod of the steam piston, the latter, 

 of course, working in its own cylinder. The steam cylinder 

 and hydraulic cylinder are therefore placed tandemwise, the 

 latter being underneath. The hydraulic cylinder is supplied 

 with water at pressure by a suitable pump, the barrel of the 

 pump being in direct communication with the hydraulic 

 cylinder, there being no valve of any kind between the 

 two. 



If we have made our explanation clear, it will be seen that 

 the ram will descend and ascend stroke for stroke with the 

 pump plunger (the same water flowing backwards and for- 

 wards continuously), it being remembered that the steam 

 cylinder has always a tendency to lift the ram. Thus, upon 

 the pump making a forward stroke, the water in its barrel is 

 forced into the hydraulic cylinder; the ram is thus forced 

 down, and gives the necessary squeeze to the work on the 

 anvil. The pump plunger then starts on its return stroke, 

 and so, by enlarging the space in the pump barrel, enables 

 the hydraulic ram to rise and press the water out of the cyl- 

 inder and back into the pump. The rising of the ram is 

 caused by the lifting action of the steam under the piston; 

 the atter. it will be remembered, being attached to the ram. 



Of course the water pressure is sufficient to overcome the 

 steam pressure on the downward stroke. 



The chief use of this press is to produce work of any given 

 thicknesses within the range of the machine. This end is at- 

 tained by regulating the volume of water used. The action 

 may be explained as follows. We will suppose, merely for 

 simplicity sake, the contents of the pump barrel to be one 

 cubic foot, and that of the hydraulic cylinder, when the ram 

 is at the full extent of its stroke, to be two cubic feet. We 

 will neglect the connecting pipe between the two, as that is 

 not a variable and does not affect the principle. If there be 

 admitted to the pump but one cubic foot of water as the 

 plunger moves forward, it will drive all this water (omitting 

 clearance) into the hydraulic cylinder, and the ram would 

 therefore only descend one-half its stroke. If the stroke 

 were two feet the travel would be twelve inches, whilst there 

 would be twelve inches of space between the anvil and the 

 lower side of the squeezing tool on the end of the ram. Ob- 

 jects of twelve inches, or above twelve inches in thickness, 

 could therefore be forged. If, however, an article six inches 

 thick had to be worked, another half cubic foot of water 

 would have to be admitted. As the pump barrel would only 

 accommodate one cubic foot of water, the extra half cubic 

 foot would remain permanently in the hydraulic cylinder, 

 and the ram would therefore not go, by six inches, to the 

 top of its stroke; in other words, the traverse of the ram 

 would be carried six inches nearer the anvil. 



It will be remembered that the upward movement of the 

 ram is effected by the steam cylinder, which is powerful 

 enough to lift the dead weight of the ram, but is overcome 

 by the hydraulic pressure. It will be seen that by regu- 

 lating the volume of water in the machine, the ram — al- 

 though always making the same length of stroke — can be 

 kept working at any given distance from the anvil: the ram 

 and pump-plunger making stroke for stroke as the water 

 flows backwards and forwards between the barrel of the 

 pump and hydraulic cylinder. The device is no less impor- 

 tant than ingenious. In ordinary forging, reliance has to 

 be placed for accuracy of work on the skill of the workman. 

 It is surprising how near perfection a good forgeman will 

 arrive by constant practice. Such men are necessarily scarce, 

 and as a consequence very highly paid, but even the nearest 

 approximation of eye and hastily applied callipers, with the 

 chance of getting a little too much work on at the last 

 minute, cannot equal the absolutely correct results of this 

 automatic system. 



ASTRONOMICAL NOTES. 



The Rev. T. E. Espin has found two new variable stars in 

 Cygnus, viz., D. M. + 36°, 3852, and D. M. + 49°, 3239. 

 They are both of a strong red color. 



The Harvard College Observatory has just issued a paper 

 entitled "Preparation and Discussion of the Draper Cata- 

 logue." The introduction to the volume contains reference 

 to the gift of Mrs. Draper of the funds by which the work 

 has been carried on, and also a description of the instrument 

 with which the photographs were taken. Then follows a 

 catalogue of the spectra of the stars. The plates were ex- 

 posed in the years 1886 and 1887. 



In the Proceedings of the Irish Academy (vol. 4, No. 4, 

 third series) Mr. J. E. Gore has a very iniei'esting paper 

 entitled " A Catalogue of Binary Stars for which Orbits have 

 been Computed." The catalogue contains 59 stars, giving 

 the name of each star, its approximate position for the epoch 

 1890.0, the elements, by whom computed, magnitude of com- 



