338 



SCIENCE. 



[N. S. Vol. XVI. No. 400. 



on the rigidity to be small but instead of 

 a large increase it is a diminution. 



The Advantages of Siamesed Hose Lines for 

 Fire Steamers: Mansfield Merriman. 

 Lehigh University, South Bethlehem, Pa. 

 The method of using several parallel lines 

 of hose from a fire steamer to a Siamese 

 joint is explained, and formula for the 

 discharge and effective velocity head of the 

 stream from the nozzle are established. The 

 effects upon the discharge and velocity-head 

 of two, four and six lines of hose are illus- 

 trated by practical examples and exhibited 

 graphically. The great increase caused by 

 two or three lines is noted, as also the much 

 smaller increase caused by additional lines. 

 It is shown that more than six lines are 

 rarely advantageous and that four lines 

 probably give the best practical results. 

 In conclusion the author briefly notes and 

 compares the analogy between the formulae 

 for the common and viscous flow of water 

 in pipes laid in parallel with that for the 

 flow of electricity in metallic conductors. 



The Nomenclature of Mechanics: R. S. 



Woodward, Columbia University, New 



York. 



The object of this paper is to advocate 

 the desirability of adopting definite and 

 •unique meanings for the principal technic- 

 al terms of mechanics, of discarding all 

 secondary meanings of such terms, and of 

 inventing new terms when essential to dis- 

 tinguish mechanical principles and proper- 

 ties differing from one another. 



On a Type of Planetary Orrery Utilizing 

 the Mechanical Principle of the Conical 

 Pendulum: David P. Todd, Director of 

 the Observatory of Amherst College. 

 This machine is intended to employ the 

 principle of the conical pendulum. Pendu- 

 lums of different length, suitable to the rev- 

 olution periods of the planets, are attached 

 at the upper end to concentric arbors, prop- 



erly geared; the spheres representing the 

 planets are attached to the lower and outer 

 ends of these pendulum rods. In this way 

 the relative periods of revolution of the 

 planets and their sizes can be conveniently 

 illustrated mechanically on as large a scale 

 as may be desired. 



The Viscous Dynamometer: J. Burkitt 



Webb. 



Some years since the author designed an 

 absorption dynamometer depending on the 

 viscosity of water for use in testing the 

 Whitehead torpedo and the results were 

 published in the Stevens Indicator. In the 

 use of it a very convenient property which 

 it possessed was discovered, namely, that 

 a sufficiently exact relation existed between 

 the moment tending to rotate it and the 

 number of revolutions, to make it possible 

 to get the horse-power from an observation 

 of the moment only. This was especially 

 valuable in Whitehead torpedo work on ac- 

 count of the engine running but a short 

 time. 



The dynamometer was redesigned three 

 or four years ago for testing turbines for 

 electric light work and is now used largely 

 for that purpose. The one first built con- 

 sists of two steel disks (circular saw blanks) 

 mounted on a horizontal revolving shaft on 

 which is journaled a cast-iron case enclo- 

 sing the disks and supporting a stationary 

 disk between them. The sides of the case 

 are also turned true so that each revolving 

 disk has a fixed surface about one eighth 

 of an inch distant from it. The case is sup- 

 plied with water which is allowed to run 

 slowly through it to prevent a rise of tem- 

 perature, and means are provided to regu- 

 late the amount of water in the case, which 

 is kept by centrifugal force in annular lay- 

 ers or disks at the other part of the case cav- 

 ity. The shaft being now connected with 

 a source of power of sufficient speed, the 

 viscositv of the lavers of water tends to 



