II. LENGTH. 53 



This instrument may be used both as a comparing apparatus, and as a 

 machine for dividing fractions of the metre, for the use of comptrollers of 

 weights and measures. A small pointer or cutter is traversed, by means of 

 a rack, along the meter, while a very simple lock action enables the milli- 

 metric displacements of the indicator to be registered without reading the 

 divisions. 



259b. Iridio -platinum Standard Metre, in course of 

 manufacture. Johnson, Matthey, and Co. 



259c. Section of Metre when finished, showing the form 

 determined upon by the International Commission. 



Johnson, Matthey, and Co. 



26O. 6-foot Measuring Hod, for uneven ground, for en- 

 gineering and scientific purposes. .Designed by the exhibitor, and 

 made by Messrs. T. Cooke & Sons. Edward Crossley. 



The apparatus consists of a wooden rod 6 ft. in length, with metal ter- 

 minations containing spherical cups fitting on to spherical heads upon tripod 

 stands. Three tripod stands are required. Each terminates in a flat ring 

 npon which the base of the short pillar carrying the spherical head is hori- 

 zontally adjustable, and to which it can be clamped. The rod is supported 

 by two tripod stands, while the third is set forward to receive the rod in 

 its next position. The inclination of the rod is read off to half-a-minute 

 in each position by means of a level and arc attached to the centre of the rod. 

 The true horizontal distance is then obtained by applying a tabulated cor- 

 rection for each inclination of the rod. 



This instrument will give an accuracy of 1 in 10,000 on any sort of 

 ground, even with a gradient of one in four. 



266. Ivory Pocket Measures. T. Hawksley. 



Containing the Fahrenheit and centigrade temperature scales ; English 

 inches divided to $ in., and centimetres divided into millimetres ; designed 

 for the purpose of introducing into everyday use the decimal system of 

 measurement. 



269. Poot-scale-plate. A rectangular brass-plate containing 

 twenty different foot-scales, made in 1769 by Adam Steitz in 

 Amsterdam. It is a copy from the original deposited in the Town 

 Hall of Amsterdam. Prof. Buys- Ballot, Utrecht. 



269a. Meter Diagram. A. and F. Stanley, Neiv York. 



289. Meter Scale with double divisions, for and 20 C., 



by Breithaupt and Son, in Cassel. 



Mathematical and Physical Institute, Marburg {Prof. 

 Dr. Melde). 



295. 2-Meter Standard Measure in steel. 



F. W. Breithaupt and Son, Cassel. 



