478 



NEGRETTI AND ZAMBEA, HOLBOEN VIADUCT, B.C. 



FIG. 2935. 



FIG. 2936. 



FIG. 2938. 



11 6 



220 440 



10 6 



3 3 



18 



2 





 



6 

 A 



be 



a. d. s. d. 



2914 Boyle's Tube, for exhibiting the comparative Specific 



Gravity of two different liquids, or the law that the 

 heights of columns of fluid which counterbalance 

 each other under the ordinary atmospheric pressure 

 are inversely proportional to the density of such 

 fluids (fig. 2914) .... 



2915 Hydrostatic Bellows, to illustrate that fluids press 



equally in all directions, and the pressure in proportion 

 to the height of the vertical column of fluid (fig. 2915) 



2916 Artificial Fountains, by Condensed Air, consisting of 



a Copper vessel, with condensing pump, and a variety 

 of jets for fragrant waters, &c., packed in case from 



2917 Extra jets for ditto, of various shapes .... 



2918 Pewter, Copper and Glass Syphons, of various forms 



(see Chemical section) (figs. 2918, 2918*) . from 



2919 Tantalus Cup, an illustration of the use of the Syphon (fig. 2919). 



small syphon is concealed within the figure, so that water may 

 poured into the glass vessel until it nearly rises to the mouth, when 

 the syphon commences to act and rapidly draws off the water 12 6 



2920 Apparatus to explain the theory of Intermitting Springs 3 10 



2921 Ditto ditto simple form in glass (fig.2921 ) 076 



2922 The B/ope Pump of Vera, or Hydraulic Belt. This machine, the use of which 



has been revived within a few years, is one of the most simple and at the 

 same time efficient of Water Elevators, and yet the most inexplicable in 

 its action. In its ancient form it consisted of a number of hair ropes 

 (for which a band of flannel or felt is now substituted), passing over two 

 rollers, one at the bottom of the well and the other at the top. By means 

 of the upper roller the band is set in very rapid motion, when the water 

 in the well adheres to its surface in a layer, which is thicker the more 

 rapidly the band moves, and becomes nearly half-an-inch thick when the 

 velocity is 1,000 ft. per minute. The water follows the band to any height 

 and is thrown off by centrifugal force in turning over the upperjroller. 



2923 Model of Chain pump 



2924 Persian or Bucket Wheel 



2925 Model of Eccentric Pump 



2926 Model of Water Pressure Engine 



Models of Nos. 2922 to 2924, constructed to order. 



