26 



74. Letcher's half guinea blowpipe cabinet in a stained 

 box. 



1880. Exhibited by T. H. and J. T. Letcher. 



75. Blowpipe cabinet. Price, 21s. 



1886. Exhibited by Townson and Mercer. 



76. Various blowpipe accessories. 



1880. Exhibited by T. E. and J. T. Letcher. 



Blowpipes at 10s. 6d., 4s. 6c?., 2s. 6d., and Sd. Hammers at 

 Is. 6cL and Is. Anvils at Is. and 6d. Forceps at 6s., 3s. 6d., 

 2s. 6d., Is. 8d, 6d. } 3d Lamps at Is., Is. in tin, lOd Steel 

 mortar at 16s. Stoneware charcoal support, 5d. Cupel strikers 

 at 6cZ. and 4cZ. Magnet and chisel at Id. each. Pestle and 

 guard ring at 6d. Platinum spoons at Is. 6d. and Is. Platinum 

 nozzles at 2s. and 4d. 



77. Pour indigo prisms. Each, 4s. 



Exhibited respectively by Reynolds and Branson, by G. 

 Mason If Co., by Townson and Mercer, and J. Preston. 

 1886. 



78. Two indigo prisms. Price, 5s. each. 



1889. Exhibited by W. Hume $ Co. 



G. Apparatus for determining Specific Gravity. 



79. Pisani's apparatus for determining specific gravity 

 by displacement. 



Lent by the Geological Laboratory, Royal College of 



1887. Science. 

 This is adapted for use with small quantities of the substance, 



or with its powder. It consists of a pair of scales, whose pans 

 are of horn, and weights, together with a specific gravity flask. 

 This is a strong bulb, with a closely fitting stopper in the form 

 of a spout, from the top of which ascends a long graduated tube 

 of narrow bore. By weighing the bulb and water first, then the 

 bulb and water with the substance placed in it, and finally the 

 same with so much water let out as brings it to its former level, 

 all the data for the determination of the specific gravity are 

 obtained. 



80. Mohr's apparatus for determining specific gravity 

 by displacement. 



Lent by the Geological Laboratory, Royal College of 



1887. Science. 



This is adapted for very large specimens. It consists of an 



inverted bell jar with stop-cock at base, supported on a wooden 



