426 
Analyses of Books. 
[July- 
Observations on Mount Etna. By S. P. Langley. 
This memoir is a reprint from the “ American Journal of Science," 
and treats on the atmospheric characfteristices of Mount Etna as 
a site for an observatory. He finds that, at the altitude of the 
Casa del Bosco (4200 feet), stars of two-thirds the brightness of 
those seen in England with the like telescopic power can be dis- 
tinguished. The gain on Etna, as compared with a lower station, 
is more in clearness of the atmosphere than in freedom from 
tremor. In solar work he distinguishes two classes of pheno- 
mena. In those of the photosphere, whether seen diredfly by the 
telescope or recorded by photography, an optical tranquillity of 
the atmosphere is of more importance than transparency. On 
the other hand, for spedlroscopic researches and for investiga- 
tions of the sun’s radiant heat, transparency is essential. 
During a few days’ stay in Egypt the definition of the sky was 
almost unequalled. From his own experience, joined to that of 
M. Janssen in the Himalayas, he concludes that the mere fadt of 
a high elevation by no means ensures good vision, though the 
chances are better at a considerable altitude, other things being 
equal. 
Report on Bisects Injurious to Sugar-Cane. By J. H. Comstock. 
Washington : Government Printing-Office. 
The species here described are Ligyrus ruficeps , a lamellicorn 
beetle of the evil family of the cockchafers (Melolonthidse). The 
insecft is about l an inch in length, and in the larval state bores 
into the stem of the cane beneath the surface of the ground. If 
sugar-cane is deficient it destroys maize. 
The “ sugar-cane borer,” Diatrce sacchari , is a moth belonging 
to the Pyralidae. It also, in case of need, extends its ravages to 
corn. The damage done by these two species, hitherto almost 
overlooked, is very serious. The general public can form, as yet, 
not the remotest idea of the percentage of agricultural produce 
destroyed by inserts. 
