38 SEC. 3. MEASUREMENT. 



189. One Ib. Avoirdupois Weight, of gun-metal, electro- 

 plated with nickel. 



Constructed as an experiment of coating brass or bronze with unoxidisable 

 metal. Oxidation, however, is found to occur at points on the surface of the 

 bronze under the nickel coating. 



190. One Kilogram Weight, of gun-metal, nickel-plated. 



191. Set of Glass Avoirdupois Weights, from 7 Ibs. to 

 1 oz., made experimentally of green bottle glass, not subject to 

 hydroscopic influences. The larger weights adjusted with lead 

 shot. 



192. Set of Metric Weights, from 1,000 grammes to 

 ] gramme. Constructed by Salleron, Paris, of opaque glass, 

 adjusted with mercury to the density of brass weights, and her- 

 metically sealed. 



193. Specimen of an Enamelled Iron Weight of 

 56 lbs, made to resist oxidation, by De Grave, Short, and Co. 



194. Specimen of a Patent Brass-cased Iron Weight 

 of 14 Ibs. 



195. Section of a Patent Brass-cased Iron Weight 

 of 14 Ibs., showing mode of construction. 



196. Copy of Standard Cubic Foot nickel-plated, with 

 filling apparatus. Constructed by G. Glover & Co. 



This is a copy of the standard cubic foot bottle, the primary unit from which 

 the gas-measuring standards were derived. It was verified by weighing its con- 

 tents of distilled water = 62 '321 pounds avoirdupois, according to Sir G. Shuck- 

 burgh's determination of the weight of a cubic inch of water. It is used as a 

 direct transferrer of a cubic foot of gas or air, which is driven out from it 

 by raising the cistern and thus introducing water from underneath up to the 

 defining line of a cubic foot. By this arrangement, the nearly undisturbed 

 surface of the water is carried upwards and gradually through the entire 

 height of the bottle, without risk of forming air bubbles. 



197. Copy of five cubic feet Gas-measuring Standard, 



made of anti-corrosive metal, by G. Glover and Co., with scale of 

 capacity graduated in feet and minute fractional parts. 



The bell is equipoised when at various depths of its immersion in the water 

 of the cistern by a balance, a portion of which hangs from a cord working in 

 a groove in the circumference of a cycloidal wheel, and attached to the axis 

 of the wheel from which the bell is suspended. 



198. Copy of a Standard Test Dry Gas Meter, with 

 testing table. Constructed by G. Glover & Co. 



Such test gas meters are authorised to be used for testing stationary meters, 

 where the larger gas measuring standards cannot conveniently be used. The 

 accompanying testing table shows it fitted with thermometers and pressure 

 gauges, and with stand pipes for outlet and inlet communications. 



