464 
DR. J. H. YIXCEXT OX THE DEXSITY AXD COEFFICIEXT 
a hundred years previously. (Musschexbeoek, ‘ Essai de Physique,’ Leyden, 1739.) 
Mairan also supported it by exjDeriments published ten years later. (Maieax, 
‘Dissertations sur la Glace,’ Paris, 1749.) But Heixrich in 1807 had obtained a 
positive coefficient. (Heixrich, ‘Gilbert’s Annalen,’ vol. 26, ji. 228, 1807.) His 
result, obtained by the direct determination of the change in length of a bar of ice, 
yields the value ’000024 as the linear coefficient for a degree centigrade. This 
observer also found the density of ice to be ’905. Thus the subject stood when 
Bruxxer commenced his experiments. 
Bruxxer started experimenting in the direction of preparing air-free ice from 
boiled distilled water, but failed to obtain it free from air bubbles. Even when he 
covered the surface of the water with turpentine immediately after boiling, the 
product had still to be rejected owing to its being full of small cracks; so that he 
was led to use selected pieces of river ice. 
The method consisted in weighing the ice in air, and in either turpentine or 
petroleum, which latter liquid had the advantages : 1. Of its smaller density ; 2, Its 
freedom from solvent action. He determined the density of the liquid by weighing 
a piece of glass in it immediately before and after weighing the ice, and he sub¬ 
sequently weighed the same j^iece of glass in water at different temperatures. He 
satisfied himself by direct experiment that by determining the temperature of the 
oil he also obtained the temperature of the ice suspended in it. The whole of the 
operations were conducted in a laboratory, the temperature of which never rose 
above freezing point. After making due allowance for the buoyancy of air, the 
re.sult for the specific gravity of ice at 0° C., referred to water at 0° C., was ’9180, 
or ’9179 as the density in grammes per cub. centim. The linear coefficient of 
expansion was ’OOOOSfo, which Bruxxer remarks was greater than that pre¬ 
viously found for any other solid. 
The paper of Petzholdt also set Struve to work about the same time 
Fig- 1- (Struve, ‘ Pogg. Ann.,’ vol. 66, p. 298). He obtained the value 'OOOOoSl 
0 for the linear coefficient per 0° C., using long bars of artificial ice in his 
./ 
G 
M 
experiments. 
Marchaxd (‘Journ. f prakt. Chemie,’ vol. 35, p. 254), using a dilato- 
meter of glass containing mercury and the ice to be experimented on, 
obtained '0000350 for the linear coefficient, but did not state the kind of ice 
used. 
The dilatonietric method was also employed in 1852 by Plucker and 
Geissler (‘Pogg. Ann.,’ vol. 86, p. 265, 1852), who determined the density 
and dilatation of artificial ice. They used a dilatometer of a remarkabl}" 
elegant design (see fig. 1). The cylinder, M, of thin glass is open at the 
liottom, and has a capillary tube, c, inside it. This tube is sealed into the 
cylinder, M, and also into the outer cylinder, N, at one end. At the other end 
of the outer cylinder was another capillary tube, and in the preliminary part 
