SCIENTIFIC SUMMARY. 
347 
that there exists a certain depending connection in the movement of the 
mean temperature of four days, placed on the ecliptic at an angle of 90° one 
from the other, for the four months (opposed two by two) of February, May, 
August, and November, which contain the critical days, known by the 
ancients under the name of the three saints of ice (May 11, 12, 13), and the 
summer of Saint Martin (November 11). In this new work he shows that 
the fact is general, and that this connection or mutual dependence of the 
four opposite days exists during the whole of the year ; whether we take 
into consideration a considerable cycle — 110 years at Berlin, 90 years at 
Vienna, 50 at London, 40 at Prague and Edinburgh, 30 at Brussels, 24 at 
Toulouse, 21 at Paris — or that we take in this point of view an isolated year 
(1864) on several European stations. The former, depending upon the same 
data, establishes, in fine, that this connection is evident also when we com- 
bine twelve by twelve the days separated one from the other by 30° of the 
ecliptic. The latter phenomenon constitutes the meteorological month , as the 
season was established by the consideration of the quadruple days. 
Alteration of the Freezing-point in Thermometers. — Dr. J. P. Fowler, 
F.B.S., has recorded an important fact in connection with the alteration of 
the freezing-point in thermometers which have been for some time in use. 
Having had in his possession, and in frequent use, for nearly a quarter of a 
century, two thermometers, of which he has from time to time taken the 
freezing-points, he thinks the results of some interest. Both thermometers 
are graduated on the stem, and are, he believes, the first in this country 
which were accurately calibrated. Thirteen divisions of one of them cor- 
respond to one degree Fahrenheit. It was made by Mr. Dancer in the 
winter of 1843-44. His first observation of its freezing-point was made 
in April 1844. Calling this zero, his successive observations have given 
0 April 1844. 
5' 5 February 1846. 
6'6 January 1848. 
6-9 April 1848. 
8- 8 February 1853. 
9- 5 April 1856. 
11T December 1860. 
11-8 March 1867. 
The total rise has been, therefore, -91 of a degree Fahrenheit. The other 
thermometer is not so sensitive, having less than four divisions to the degree. 
The total rise of its freezing-point has been only *6 of a degree ; but this is 
probably owing to the time which elapsed between its construction and the 
first observation being rather greater than in the case of the other thermo- 
meter. The rise of the two thermometers has been almost identical during 
the last nineteen years. 
Crystalline Refraction. — M. A. Cornu has written a memoir on this sub- 
ject, in which he propounds a new theory of Fresnel’s law of crystalline 
refraction. The principal conclusions of the report in his memoir were, that 
the luminous vibrations were normal to the plane of polarisation, as Fresnel 
and Cauchy announced a long time ago, though the direct proofs hitherto 
proposed are open to discussion. 
