364 



SCIENCE. 



[N. S. Vol. XIX. No. 479. 



about fifteen arches, Mr. Edge suggests a 

 method of procedure which he has found 

 to be the most simple, and hopes that some 

 one else will be interested in extending the 

 investigations. The paper will probably 

 be published in the Transactions of the 

 American Society of Civil Engineers. 



Professor Henry S. Jacoby then gave an 

 account of ' The New Features and Tenden- 

 cies in Bridge Engineering' which he had 

 observed in his very extensive bridge in- 

 spection tours which he has had the priv- 

 ilege of taking during the sabbatical period 

 which was granted to him by Cornell Uni- 

 versity. He noted the increase in the use 

 of plate girders up to those of 128 feet 

 4 inches from center to center of supports ; 

 that the present tendency in railroad 

 bridge construction seemed to be to get 

 rid, so far as possible, of the overhead 

 portions of bridges; that riveted trusses 

 were now built in spans up to 230 feet; 

 that the length of panels had now been 

 increased to 37 feet, and mentioned bridges 

 over the Monongahela and Allegheny Elvers 

 of the Pratt type, with curved upper chords 

 having only 11 panels in 417-foot spans. 

 The maximum span of simple trusses is 

 still the same as it was ten years ago, the 

 record being held by the Louisville bridge 

 of 546 feet 6 inches. The Pratt truss seems 

 to be in the ascendency in both riveted and 

 pin construction. The author stated that 

 the majority of the masonry now being con- 

 structed by the railroads, with one notable 

 exception, is of concrete, and that concrete 

 arch bridges had been built with spans up 

 to 130 feet. Professor Jacoby has evidently 

 improved his opportunities during the past 

 year, and his work as an instructor must 

 of necessity be correspondingly benefited 

 by the opportunities which he has accepted 

 for studying bridges in the drawing-room, 

 in the shop, in the field a,nd in use. 



The next two papers presented were from 

 the Ohio State University, at Columbus, 



Ohio. The first one was by Professor Wm. 

 T. Magruder, and described 'An Hydraulic 

 Micrometer Caliper' which was presented 

 for inspection to the section. This caliper 

 consists of a bronze graduated circle sixteen 

 inches in diameter which is secured to the 

 end of a hydraulic drum connected to a 

 stand-pipe, and so that it can be rotated 

 around its axis. Cross-screws, both radial 

 and axial, are carried by the revolving ring 

 so that pointers fixed in the ends 'of the 

 axial screws can be brought into contact 

 with the surface of a jet of water issuing 

 from the orifice, and so that by means of a 

 scale on the screws all the coordinates of 

 the jet can be obtained for a distance of 

 six inches or more from the entrance to 

 the orifice. 



Professor James E. Boyd and Professor 

 Horace Judd presented a paper describing 

 and giving the results of their experiments 

 with 'Pitot Tubes,' and on 'The Experi- 

 mental Determinations of the Forms of 

 Water Jets. ' The paper describes ' ' a Pitot 

 tube as a simple contrivance for measuring 

 the velocity of water. It consists of a small 

 tube placed in the stream so that the water 

 strikes fairly against one end. Some dis- 

 tance from the end it is bent and connected 

 to a vertical glass tube. The current 

 striking against the end produces a pres- 

 sure which is measured by the height to 

 which water rises in the glass tube (or, in 

 case of high pressures, by a gauge of some 

 sort). Pitot claimed that this height was 

 equal to the distance a body must fall to 

 acquire a velocity equal to that of the 

 stream. Later observers have thought that 

 this is incorrect, and that the water rose 

 much higher. These experiments were 

 with jets, and showed that Pitot was prac- 

 tically correct. Incidentally it was found 

 that the contracted vein in a jet of water 

 from an orifice in a thin plate is about 

 .785 of the diameter of the orifice, and that 

 the velocity of such a jet is over 99 per cent. 



