METEOROLOGY. 223 
not more than two and a half lines in thickness, always opake, and of 
snow-white color, occurring in wintery weather. 2d. Hay, properly so 
called, consisting of granules of spherical, paraboloidal, or pyriform shape. 
varying in size from a cherry-stone to a walnut. These have generally a 
point, opposite to which is a hemispherical segment, and in their centre is 
an opake nucleus of one half to two lines in diameter. This species occurs 
generally in summer, in connexion with thunder and lightning. The two 
kinds, however, according to Kaemtz, differ only in size. As a third and 
very rare species Arago considers those granules which never have a 
nucleus of snow, and differ from sleet of equal size by being transparent. 
These are unquestionably produced by the freezing of drops of rain in 
falling from a cloud into a stratum of colder air. | 
The form of true hailstones is very various ; generally they are rounded, 
sometimes flattened or angular. Delcross supposes the most common form 
to be a three-sided spherical segment, produced by the shattering of larger 
spheres. Hailstones of different forms are represented in pl. 23, figs. 24-35. 
The internal structure is almost as various as the form; sometimes alter- 
nations of transparent and opake strata are observed. The diameter of 
simple hailstones at a mean latitude, according to Muncke, is not over one 
and a half or one and three fourths inches, larger masses appearing to be 
produced by the aggregation of individual stones. Instances of hailstones, 
the size of hens’ eggs or larger, are not rare in some parts of the world. There 
are cases on record of vastly larger hailstones than those just mentioned ; 
most of these, however, are of a very fabulous character. Thus in 1719 
hailstones fell at Kremo weighing six pounds, and at Namur, in 1717, 
weighing eight pounds. According to Wallace, pieces of ice a foot thick 
fell in the Orkney Islands in 1680; in 1795 pieces of ice, six to eight inches 
long, and two fingers thick, fell in New Holland. According to public 
prints, a lump of ice fell in Hungary on the 28th of May, 1802, three feet 
long, three feet broad, and two feet thick, estimated to weigh 1100lbs. In 
the latter part of the reign of Tippoo Saib, a lump of ice the size of an 
elephant fell near Seringapatam. In all these cases the mass of ice most 
probably consisted of an aggregation of single lumps frozen together on the 
ground. It is only rarely that foreign substances have been found in hail- 
stones. In 1755 these fell in Iceland containing sand and volcanic ashes ; 
in Ireland, in 1821, hail with a metallic nucleus, recognised as sulphuret of 
iron ; in 1824, in Siberia, hail containing octahedrons resembling auriferous 
pyrites. According to the earlier observations, small pieces of chaff are 
often found in hail. 
Hail generally falls during the day, although the idea that it never falls 
by night is erroneous, there being well authenticated cases to the contrary. 
[tis very probable that the rarity of night hail is only apparent, not real, 
and owing to the greater difficulty of observing such phenomena during the 
darkness. It has already been mentioned that the smaller hailstones 
generally fall in spring: in Germany in April, during that condition of the 
weather known as April weather. Short showers of cold rain then alternate 
with warm sunshine, and with the rain there fall either single hailstones, 
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