86 SEC. 3. MEASUREMENT. 



vessel, whereas the bathometer gives the mean depths taken over a certain 

 area, depending for extent upon the depth itself. 



It is thought that the bathometer may render useful service to the mariner in 

 warning him of changes of depth long before reaching dangerous ground ; 

 and the position of a vessel, when no astronomical observations can be taken, 

 may be ascertained by means of a bathometer, provided the contour lines of 

 equal depths of oceanic basins were accurately laid down. 



4:21 c. Graphical Bathometer, after von Jolly. 



University of Munich. 



423. Apparatus for determining the elasticity, strength 

 of traction, and columnal strength of woods and timber. 



Prof. Dr. Nordlingrer, Stuttgart. 



42 3a. Apparatus used for experimenting on the 

 Flexural and Torsional Rigidity of Solids, by Professor 

 Everett, and described in the " Transactions of the Royal Society," 

 1866, p. 185. Sir William Thomson. 



424. Apparatus for determining the relative strength of 

 flexure, and the elasticity of woods and timber. 



Prof. Dr. Nordlinger, Stuttgart. 



425. Hydrostatic Apparatus for ascertaining the specific 

 weight of woods. Prof. Dr. Nordlinger, Stuttgart. 



42 5a. Registering Statical Gauge for Pressure in 

 Guns. System of W. Paschkiewitsh. 



Captain W. Paschkieivitsh, St. Petersburg. 



426. Thurston's Testing Machine, invented by Professor 

 Thurston, of Steven's Institute of Technology, Hoboken, U.S.A. 



This machine is used for testing the limit of resistance, ductility, and homo- 

 geneousness of iron, brass, steel, and other materials of construction. By 

 means of an ingenious but simple arrangement, a permanent diagram of the 

 behaviour under varying conditions of the materials can readily be obtained. 



W. H. Bailey and Co., Manchester. 



42 6a. Machine for measuring the slipping between hard 



surfaces rolling in contact. Prof. Osborne Reynolds. 



This machine was constructed for the purpose of verifying the conclusions 

 of the exhibitor respecting rolling friction, and the existence of a certain 

 amount of slipping between two smooth surfaces of different curvature, or diffe- 

 rent hardness, when the one rolls on the other under pressure. It has also been 

 used to measure the slipping between the surfaces, when the one is driving 

 the other against various resistances and at various speeds, as well as the 

 wear of the surfaces. 



The large rolling surface is of cast-iron, supported so that it can rotate 

 freely, but otherwise rigidly fixed. For the smaller surface various materials 

 have been used, that exhibited being of steel ; this cylinder is supported so 

 that while its axis is always parallel to that of the larger cylinder, it can be 

 pressed against the larger cylinder with various degrees of pressure by means 

 of a lever acting through friction rollers. Arrangements are made for 

 recording the number of revolutions of both cylinders ; and connected with 



