100 J. Schiel on the Distillation of Common Rosin, 
We see in this table abundant evidence that the frequency of 
lightning depends upon other circumstances than simply latitude, 
Throughout the western half of the Atlantic Ocean, lightning 
occurs three times as frequently as throughout the eastern half of 
that ocean. If we take the average of all the observations upon 
the same parallel of latitude, we shail find the number of days 
of lightning to be as follows: 
) North Atlantic. South Atlantic, 
From lat. 0 tolat. 5° 20 wre 
“ “ 5 “ 1 0 1 q 2 
- saci § aoe ag 15 14 1 
Aid “ ] 5 “ 20 8 2 
“ “ 20 “ 25 T 6 
me waite FSS a 30 19 9 
s #80...) & 85 19 q 
= sR Gas 40 19 6 
“ “ 40 “ce 4 5 1 5 9 
. “ 4 5 “ 5 0 5 8 
“o “ 50 “ 5 5 5 8 
“ “ 5 5 “ 60 4 4 
The average frequency of lightning in the North Atlantic is 
two and a half times as great as in the South Atlantic; also the 
average frequency of lightning on land, at least in the northern 
hemisphere, appears to be more than twice as great as in the North 
Atlantic. The bearing of the preceding facts upon the theory 
of auroras will be considered hereafter. 
pee 
Arr. XII:—On the Products of the Distillation of Common 
fosin ; by JAMES Scuren, of St. Louis, 
THE chemical process taking place in the distillation of com- 
mon rosin or colophony, and the two different liquids which are 
obtained by that distillation, have as yet escaped the attention 
of chemists; the whole process is almost completely wrapped in 
darkness. The two liquids just mentioned are distinguished as 
essence of rosin (in Europe “ German oil of turpentine”) and rosin 
oil; the former is thin, of a light yellow color, and a strong, 
almost aromatic odor; the latter is a thick liquid of a somewhat 
: sa | pee odor. 
he essence of rosin is a mixture of two substances, which may 
D 
very thin, perfectly colorless and transparent, and of a strong, 
refracting power. I call it colophonon. The specific gravity 0 
