474 



NEGEETTI AND ZAMBRA, HOLBORN VIADUCT, B.C.. 



FIG. 2870. 



FlG. 2893. 



Each. 



Each. 



2886 Windmills or Fans, of a superior construction, with 



shifting vanes to show the resistance of air (fig . 2886) 



from 



2887 Four Barometer Tubes, for showing the upward, down- 



ward, oblique, and lateral pressure of the atmosphere 

 2887* Leslie's Apparatus for Freezing Water by evaporation 

 under an exhausted Air- Pump receiver 



a. 



2888 



2889 



2890 



2891 



2892 



2893 



220 



10 6 



1 10 



A thin film of ice may be formed by this apparatus in the warmest weather. Leslie's apparatus 

 is the basis of many forms of Ice Producing Machines of the present day. Leslie's Experiment 

 was first made in June, 1810, and is the converse of the experiment, No. 2859, page 471, viz., the 

 production of heat by rapid compression. 



Apparatus, consisting of three glass vessels, for illus- 

 trating the mechanical properties of air . 



Glass Flask, mounted with Brass Stopcock, for illus- 

 trating the influence of diminished pressure in 

 facilitating ebullition (fig. 2861) . 



Philosophical Water Hammer, (fig. 2 890), for exhibiting 

 the force f and solidity with which water falls in a 

 Yacuum . 



Water Hammer, Y shaped, closed at one end, and 

 having a brass mounting and stop-cock at the other 

 for exhaustion by the Air Pump (fig. 2891) 



BaUoons of Gold Beaters' Skin, for filling with 

 Hydrogen Gas from 



12 6 



12 6 15 



046 



7 6 



12 6 



036 



Apparatus for demonstrating the pressure of the atmosphere to be about 

 ]5 Ibs. upon the square inch [of surface, an improved form of the Magde- 

 burgh Hemispheres. A brass box, one inch square, is fitted with a ground 

 metal cover, and also a stopcock. When exhausted of air, the cover can 

 be connected to a steelyard, which shows that a force equal to about 15 Ibs. 

 is required to remove the cover of the box; mounted on a convenient 

 stand (fig. 2893) 3 10 



This apparatus is so constructed that the exhausted box can be screwed into the cross bar on top 

 of the upright pillars, and by means of the pulley and cord and a weight, it can be demonstrated 

 that the pressure on the lid of the box is similar in both positions. 



