SCIENTIFIC EXPERIMENTAL APPARATUS. 443 



gatious from using iiucompared thermometers ')nay amount to two per 

 cent. 



50. Bowland's apparatus for determining change of specific heat of liquids 

 with temi)erature. Constructed by Schneider. 



51. Dulong''s apparatus for the heat of combustion, Salleron, Paris. 



52. MellonPs apparatus for radiant energy, Salleron, Paris. 



53. Two instruments for the calibration of mercurial thermometers, one 

 by Golaz and the other by Salleron. 



54. Eoicland's apparatus for determining the mechanical equivalent of 

 heat, or for investigating the specific heat of liquids and their change 

 with rise of temperature. 



This instrument was constnicted by the aid of funds contributed by 

 the Eumford committee of the American Academy of Arts and Sciences, 

 but the instrument will remain for the present at Baltimore. It was 

 constructed by Schneider. It is run by a petroleum engine, No. 66 below. 



To be constructed soon : * 



Api)aratus for compressing gases to 1,000 atmospheres. 



Apparatus for accurately determining the form of the adiabatic curve 

 of gases and vapors at any temperature up to about 100° C. 



MISCELLANEOUS. 



55. Comparator, by Meyerstein, for bars 1 metre long. Microscopes 

 cannot be set nearer than 10 centimetres. One division of head of 

 micrometer screws is about 1-700 millimetre. 



56. Microscope comparator, designed by Eowland after Eogers's plan, 

 and made by Grunow. 



57. Dividing engine, by Perreaux. Free motion about 55 centimetres. 

 Screw, h, millimetre thread. Head divided into 250 i)arts. 5.1 divisions 

 of head gives 1 millimetre almost exactly. Subsidiary screw at right 

 angles to other one. 



58. Air pumps. — Eotary and common, by Eitchie, of Boston ; mercury, 

 on Jolly's plan, by Berberich, of Munich. 



59. Rotary pump for compressmg gases to 15 atmospheres. Golaz, 

 Paris. 



60. Three mercury gauges; one about 25 metres high, and measuring- 

 pressures vq) to about 33 atmospheres; one movable and measuring 

 pressure from 1 to 4 atmospheres ; and one measuring from to 1 atmos- 

 phere. 



61. Barometer, by James Green, of New York, with very large tube. 



62. Tico cathetometers ; one by Meyerstein and the other by Salleron. 



63. Standard metres, compared at Washington. 



64. Balances and weights. — One balance weighing to 5 kilos, and accu- 

 rate to about 1 mg., with weights from 5 kilos, to 1 mg. One weighing 

 "to 200 grms, accurate to about 0.1 mg., with weights from 100 grs. to 1 



* Nos. 18, 24, 25, and 27, aud the silvered scale of No. 39, belong to Professor Row- 

 land, but are used iu the laboratory. 



