A physical treatise on electricity and magnetism: By J. E. H. Gordon, B. A. Camb., Assistant Secretary of the British Association. 2 vols., 8vo. New York: D.Appleton & Co. 1880.

• Book ID: 103087843
• Publisher: Elsevier Science
• Year: 1881
• Tongue: English
• Weight: 263 KB
• Volume: 111
• Category: Article
• ISSN: 0016-0032
• DOI: 10.1016/0016-0032(81)90445-2

✦ Synopsis

I, en~;h of J'upiter's ]}ay.--The Emperor of Brazil has transmitted to the French Academy a note of M. Crul's upon the time of Jupiter's rotation. The sharpness of outline and the bright color of the brown spot which has been so long visible enabled him to deduce from nearly 1100 rotations a period of 9 h. 55 m. 36 s.--Comptes 3~endus.

C.

Optical Telegraphy.--A. Crova describes an apparatus for sending light signals, which he invented in conjunction with Le Verrier, in 1870, and which he regards as substantially identical with Mercadier's, the principal difference being that he used oil instead of petroleum. The signals were visible in broad daylight, and when the sky was somewhat clouded correspondence could be carried on by day as well as by night. He found it necessary to employ oxygen under a feeble pressure, and to have the manipulating key armed with a strong string, so that it could be suddenly opened and closed. Without this precaution the signal would overlap and produce eonfitsion.--Comptes /~endus. C.