September 19, 1884.] 



SCIENCE 



291 



ing, the pictures being delivered the same night. 

 The dynamo is run by a gas-engine; and it was stated 

 that more light could be thus bad from gas, than by 

 burning it directly. Sixteen feet of gas per hour will 

 develop one horse-power. 



Dr. W. A. Traill had a paper on the Portrush and 

 Giant's Causeway electric tramway; and Mr. H. 

 Smith, one on electric tramways. The former was 

 accompanied by a working model. A review of pre- 

 viously constructed roads was given, and the points 

 of difference emphasized; and the commercial suc- 

 cess of the road was announced. Owing to the 

 interest created by this paper, and the first two, Pro- 

 fessor Thompson's paper on dynamo-electric ma- 

 chines was left over. 



Mr. C. J. H. Woodbury described the ' automatic 

 sprinkler ' system in an American mill, and referred 

 to a slow-burning construction of the latter, where 

 heavy beams, widely separated, support a three-inch 

 planking, on which is laid the flooring of hard wood. 

 A large number of sprinklers have been critically 

 compared in the interest of the insurance companies; 

 and the result of this work showed a record favorable 

 to the value of the apparatus, as it had operated 

 in one hundred and forty-one mill fires, without any 

 instance of total failure except in two instances, 

 where the water supply had been shut off from the 

 system. The sprinklers were tested for sensitiveness 

 by exposing them to a jet of steam instead of a fire, 

 because the former is more regular in its action. The 



resistance of the soldered joints to shearing-stress was 

 exceedingly variable, ranging from twenty-five hun- 

 dred to seven thousand pounds per square inch. 



The first attempts to make sprinklers were devoted 

 to endeavors to construct an arrangement for rigidly 

 holding a valve to a seat; and, after these had proven 

 failures, the method of soldering a cap over the 

 sprinkler was next introduced. Later, Mr. F. Grin- 

 nell solved the problem, by placing the valve in the 

 centre of a flexible diaphragm; and the arrangement 

 of the parts was such that the water- jjressure kept 

 the valve shut until the soldered joint leaked, and 

 then this same pressure forced the sprinkler open. 



Professor Osborne Reynolds discussed the ' friction 

 of journals.' The report of a committee on lubrica- 

 tion was referred to, and various methods of lubrica- 

 tion discussed. The method giving the best results 

 is to let part of the shaft run in a bath of oil, which 

 is then sucked in by the action of the shaft. With 

 oil fed by a siphon or a plain hole, the friction is 

 seven or eight times greater; and, in one experiment, 

 the oil was forced out of the hole with over two hun- 

 dred pounds pressure on a square inch. Professor 

 Thurston was called upon, and gave his experience 

 with lubricants, confirming the statements of the 

 paper, and referring to a case in which he had used 

 a pump to force oil to the journals. Evidently, if so 

 much friction can be saved by copious and regular 

 oiling, it might pay to supply journals systematically 

 with oil under pressure. 



AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 



PROCEEDINGS OF THE SECTION OF 

 MATHEMATICS AND ASTRONOMY. 



The first paper read in this section was by Prof. 

 E. C. Pickering, upon the colors of the stars. The 

 need of exact photometric measurement of different 

 parts of their spectra was first pointed out, and the 

 author then described a very ingenious method of 

 accomplishing this. In the telescope tube, a little 

 beyond the focal plane, is a direct vision prism, so 

 set as to give a spectrum extended in declination; 

 and on the preceding side of this prism is placed a 

 piece of plane glass, whose edges are so ground, that, 

 when a small portion of the following side of the 

 cone of rays falls upon it, it gives a small white 

 ghost, just preceding the spectrum and always oppo- 

 site the same wave-length. In the focal plane is one 

 of Professor Pritchard's neutral-tint wedge photome- 

 ters, and behind it a thin metal diaphragm with four 

 long narrow slits parallel to the equatorial motion; 

 so that, when the spectrum transits behind them, 

 four little stars — a red, yellow, blue, and a violet — 

 shine through these slits, and the time of the disap- 

 pearance of each, as they move towards the thicker 

 edge of the wedge, measures its brightness. From 

 these time3 may be deduced the magnitude and color 

 curve of the star. To fix the same wave-lengths for 



each observation, the little white ghost is adjusted 

 upon one of two parallel wires, which project out be- 

 yond the preceding side of the diaphragm. For a suc- 

 ceeding transit, the ghost is adjusted upon the other 

 wire, half a slit-interval distant, and thus eight points 

 of the spectrum are photometrically measured. Pro- 

 fessor Young, of Princeton, spoke very highly of the 

 ingenuity and effectiveness of the device, especially 

 for the systematic measurement of a large number of 

 stars. He pointed out, however, what might be a 

 source of error; viz., the different sensitiveness of 

 different observers' eyes to different colors, so that 

 they would probably observe the times of disappear- 

 ance of the four colored stars relatively slightly dif- 

 ferent. 



The next paper, by Professor Daniel Kirkwood, 

 discussed the question whether the so-called ' tempo- 

 rary stars ' may be variables of long period, referring 

 to the sometimes-claimed identity of the temporary 

 stars of 945 and 1264 with the well-known Tycho 

 Brahe's star, which blazed forth in Cassiopeia in 

 1572, and whose position is pretty closely known from 

 his measures. The conclusion reached was, that on 

 account of the sudden apparition of the temporary 

 stars, the short duration of their brightness, and the 

 extraordinary length of their supposed periods, they 

 should be considered as distinct from variables. 



