204 L. CASELLA'S CATALOGUE 



2365. PHOTOMETER as No. 2364, in polished mahogany case with glazed front 550 



2366. PHOTOMETER (WHEATSTONE'S), for estimating the relative value of two lights. It 



is founded on the principle of their intensities decreasing according to the 

 squares of their distances, so that the bead disc being made to revolve, and the 

 distance of each measured from the instrument, the relative value of each light 

 may at once be known (fig. 2366), p. 203 . . 180 



2367. THE SAME, with a variety of silvered bead discs, which, when applied, present an 



almost endless variety of eliptical curves and brilliant lines of light 1 15 



2368. Cooper's Tube Apparatus, consisting of graduated glass tube with water 



cylinder, water dish or pan, flexible tube with glass end and pipette for re- 

 agents, the tube -being of Mann's improved form, with opening at bend, by 

 which the difficulty in using these tubes is entirely obviated 1 10 



By means of this apparatus an expeditious and inexpensive analysis of gas sufficiently 

 correct for all practical purposes may be readily obtained. 



2369. COOPER'S TUBE, as above, improved by Mr. Mann, engineer of the City of 



London Gas Works . . . . . . 076 



2370. SULPHUR TEST (LETHEBY'S), viz., glass condensing cylinder and combustion tube, 



long outlet tube, glass funnel with metal end-piece and ammonia bottle, 

 complete on polished wood stand . . . . 2 10 



2372. MANN'S IMPROVED THOMPSON'S APPARATUS for testing the heating power of 



fuel. This ingenious and practical apparatus consists of a combination 

 cylinder with movable weighted base, small copper furnace with tube 

 and tap, and 5 spare taps, 2 short glass water tubes, graduated to 29,010 

 grains, small sensitive thermometer in copper case, 3 Mann's protective 

 diaphragms, scales with grain weights, small iron pestle and mortar, hair 

 sieve and canister with oxygen mixture, in polished mahogany case with 

 drawer, lock, and key . . . 550 



2373. Testing Gas Holder, of best make, to hold 2 cubic feet, with copper bell and 



double divided scale, balance wheel on friction rollers, cycloid and weights, 

 gun metal inlet and outlet cocks, and pressure gauge complete, handsomely 

 japanned, suitable for a laboratory . . v 18 10 



2374 TESTING GAS HOLDER, for testing meters, as above, to hold 5 cubic feet, with 

 cast-iron tank, bell with scale, double divided to 5ths and l-100ths, cycloid and 

 weight, balance weights, 3 tube pressure gauge, etc., warranted to give the 

 same continuous pressure, handsomely painted and accurately adjusted 



28 



2375. TESTING GAS HOLDER, as above, to hold 10 cubic feet, very perfect and complete 



38 



GAS APPARATUS, GAS TUBING, AND APPLIANCES, in every variety, on the best 

 term*. 



MECHANICAL AND DYNAMICAL APPARATUS, 

 GEOMETRICAL FORMS, ETC. 



The models, etc., quoted in this section include only such as will be found of value 

 to the teacher and student of the laws and science of motion and mechanics, besides 

 their use in these studies, the solids form excellent drawing models, owing to the- 

 symmetry of their shape and the variety of shadows which each object aifords. 



