132 Proceedings of Boy al Society of Edinburgh. [mar. 21, 
And he refers more particularly to the cryoliydrate of Na 2 S0 4 
forming and melting at - 0 o, 7. 
Now the bearing of Guthrie’s experiments is to show that, while 
at sufficiently low temperatures, and with suitable concentration, 
the water will solidify along with one or other of the salts in solu- 
tion, until this low temperature and high concentration are attained, 
pure ice must be the result of freezing. 
The abnormal phenomena attending the formation and the melt- 
ing of ice in saline solutions and sea-water find a natural explana- 
tion in an observation which I have frequently quoted, and which 
Dr Pettersson mentions in a footnote at p. 318, namely, that “ a 
thermometer immersed in a mixture of snow and sea-water which is 
constantly stirred indicates - 1°'8 C.” If this is true, it is clear that 
my melting-point observations proved nothing. On repeating the ex- 
periment I found it confirmed, and took the opportunity this winter 
of investigating the matter more closely. The paper now communi- 
cated to the Royal Society of Edinburgh contains the first portion of 
the results. It deals with the subject under two heads, namely, (a) 
the temperature at which sea-water and some other saline solutions 
freeze, and the chemical constitution of the solid and the liquid 
into which they are split by freezing ; and ( b ) the temperature at 
which pure ice melts in sea-water and in a number of saline solu- 
tions of different strengths. 
(a) The freezing experiments were limited to sea- water and solu- 
tions of NaCl comparable with sea-water. 
Chloride of Sodium . — Four solutions were used, and they were 
intended to contain 3, 2*5, 2, and 1’5 per cent. NaCl respectively. 
Forty grammes of this solution, in a suitable beaker, were immersed 
in a freezing mixture of such composition as to give a temperature 
from 2° to 2° ’5 C. below the freezing temperature expected. The 
temperature at which ice began to form (if necessary after adding a 
minute splinter of ice) was noted, and the freezing was allowed to 
continue with constant stirring till the temperature had fallen 0 o, 2 
C. A specimen of the mother-liquor was removed, and the chlorine 
in it determined ; the chlorine in the original solution had been 
determined before. The beaker was then removed from the freezing 
bath and allowed to melt. The temperature in all cases rose during 
melting exactly as it had fallen during freezing. In the following 
