472 



NEGRETTI AND ZAMBRA, HOLBOBN TIADUOT, B.C., 



FIG. 2881. 



FIG. 2874. 



FIG. 2882. 



Each. 

 s. d. 



Each. 

 s. d. 



3 15 



076 12 6 



2863 Scale Beam and Stand, fitted with a light Glass Vessel 



graduated in Cubic Inches, by which a number of 

 most instructive experiments can be exhibited, illus- 

 trating the specific gravity or weight of various fluids 

 and gases ..... .... 



2864 Filtering Cup, with ground Brass Plate, for. showing 



the porosity of wood, without receiver (fig. 2864) . 



2865 Fruit or Taper Stand, for supporting shrivelled fruit, 



&c., under the receiver of an air pump ... 036 



2866 Fountain in Vacuo (fig. 2855) ..... .076 0150 



2867 Tall Fountain Glasses ....... 10 6 



Bladder Glass (fig. 2868) ...... 036 050 



Hand Glass (fig. 2869) ....... 020 040 



2870 Bell Experiment, illustrating that air is essential to 



sound (fig. 2870) ........ 10 6 



2871 Ditto, best make, with a ratchet motion (fig. 2871) . 186 

 2871* Bell Experiment, fitted with electro-magnetic break for 



ringing the bell by a galvanic battery ... 330 



2872 Madgeburg Hemispheres (fig. 2872), the invention of Otto de Guericke 



(1654), for illustrating the pressure of the atmosphere : 



Small, 16s. Second size, 18s. Third size, 30s. 



2873 Torricellian Experiment, for illustrating the pressure of the atmosphere and 



construction of the barometer, simple form ..... 15 6 



2874 Ditto ditto larger, with graduated tube, best mounting and receiver, 



&c. (fig. 2874) ........... 220 



At pages 2 and 3 will be found a full description of Torricelli's celebrated experiment, and also the 

 construction of Standard Barometers. 



