OF ELECTKICAL INSTKUMENTS. 



169 



1949. IMPEOVED PHOTOSTAT, by which a 



powerful and uniform light is unin- 

 terruptedly maintained 990 



ELECTROMETERS, etc., for measuring eleo 

 trical tension : 



1950. CAVALLO'S PITH BALL ELECTEOMETEE 



(fig. 1950), p. 170 090 



1952. HENLEY'S QUADEANT ELECTEOMETEB, 



with boxwood graduated arc, 3s. 6d. ; 

 with ivory arc (fig. 1952), p. 170 

 076 



1953. BENNETT'S GOLD LEAF ELECTEOMETEE 



(fig. 1953), p. 166, with an improved 

 mode of insulation and stand, with \ 

 pint, 1 pint, and 1 quart jars, 6s., 11s., 

 15 



1954. SINGEE'S ELECTEOSCOPE, with conden- 



sing plate and joint 1 17 6 



1955. HATTY'S NEEDLE ELECTEOSCOPE. This 



portable and delicate instrument is 

 employed chiefly in ascertaining the 

 electrical state of mineral substances 

 080 



1956. HAEE'S SINGLE LEAF ELECTEOSCOPE, 



15s. to . . 100 



1957. Tate's Electroscopes, viz., small collec- 



tion as described in Tate's " Electri- 

 city," per box . 076 



1958. GUTTA-PEECHA INSULATING SUPPOETS, 



FIG. 1948. 5 inch, high, with needle tops for the 



above, per pair , . . . . 016 



1959. GUTTA-PEECHA INSULATING SUPPOETS, with flat tops, per pair 016 



1260. LANE'S DISCHAEGING ELECTEOMETEE, large size with jar . 0126 



1962. Cuthbertson's Discharging Electrometer . , , 2 10 



1963. COULOMB'S TOESION ELECTEOMETEE, for measuring small quantities of electricity 



with precision and its attractive and repulsive force (fig. 1963), p. 170, from 



1 15 



1964. HAEEIS'S UNIT JAB ELECTEOMETEE, with graduated slide for charging other 



jars or batteries with known proportion of electricity 1 10 6 



1965. HAEEIS'S BALANCE BEAM ELECTEOMETEE, for estimating in grains the attractive 



force exerted between two surfaces oppositely electrified, as the outer and inner 

 coatings of a battery or Leyden jar (fig. 1965), p. 170 . 3 18 



