116 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



1736. Chnstin having introduced into a tube terminated 

 by a bulb a quantity of mercury, whose volume might be 

 represented by 6600 at the temperature of freezing water, 

 found that this volume became 6700 when the tube was 

 plunged into boiling water. The alcohol of the original 

 thermometer being thus dilated 100 parts, Christin divided 

 the corresponding space passed over by the mercury into 

 100 equal parts, remarking that these new divisions, being 

 smaller than those of Reaumur, would be more in harmony 

 with the sensations caused by variations of temperature. 

 Such was the origin of the Centigrade thermometer, which 

 was afterward known for a while under the name of the 

 "Thermometer of Lyons." Four years after that is to say, 

 in 1746 Cassini, who was a well-known optician at Lyons, 

 had sold seven hundred of these in Paris, besides others in 

 Provence and Dauphiny. 13 j5, III., 94. 



TERIODICITY OF HAIL-STOKMS. 



The tendency which has been so marked of late years to 

 look for a periodicity in almost every natural phenomenon 

 corresponding to the periodical increase and decrease of the 

 solar spots, seems to have been carried to its fullest extent 

 in the recent suggestion of Professor Fritz, according to 

 whom the frequency of hail-storms has some connection, ac- 

 cidental or otherwise, with the frequency of solar spots. He 

 finds, by collecting the records from twenty -five different 

 European and other stations, that all observations show that 

 the years of greatest frequency since 1806 have been 1817, 

 1830, 1838, 1848, and 1860, which years follow or are nearly 

 coincident with the sun-spot maxima of 1817, 1829, 1837, 

 1849, and 1860; whence it would follow that the year 1871, 

 a year of sun-spot maximum, should be also a year of fre- 

 quent hail-falls, as actually was generally recorded. Further- 

 more, seasons of infrequent hail-storms correspond to the min- 

 imum of solar spots, as in 1810, 1823, 1834, 1844, and 185G. 

 It has also been often remarked that a winter of extensive or 

 frequent auroras is followed in the succeeding summer by 

 unusual hail-storms. The connection between auroras, light- 

 ning, hail, and cirrus clouds and the solar spots seems, there- 

 fore, worthy of further study. 7 C, XV., 244. 



