74 
POPULAR SCIENCE REVIEW. 
declination circle is intended to be read off from the same part. 
In the same case in the gallery in which this great object-glass 
is exhibited, there are other specimens of lenses, also ground 
and polished by Wray, all of which (including a 9-inch and 5-inch 
glass) have been equatorially mounted by Mr. Buckingham for 
his particular use. The simplicity and steadiness of the port- 
able stand, and the beautiful workmanship of the 7-foot tele- 
scope, will be much admired. We may congratulate Messrs. 
Buckingham and Wray upon their remarkable success in this 
branch of optics, and upon the introduction into England of a 
perfection in telescopes, both as regards size and capability, 
which had hitherto been monopolized by the Munich artists. 
The difficulty of obtaining a fixed position, either for an 
observer or his instrument, on board a rolling ship, has often 
been endeavoured to be rectified, but hitherto without success. 
Chairs, suspended like a chronometer in numerous gymbals, 
have not been found sufficient to give the necessary steadiness. 
Peg-tops, with a plane mirror on the upper part, spun on the 
deck of a ship, have been used in order to give a fixed horizon. 
Professor Smyth has turned the gyroscope, or rather the 
principle of free rotation, to account in an instrument con- 
structed by him, and tried with success on his journey between 
Leith and St. Petersburg. With this gigantic instrument, 
which required to be set in motion by the combined action of 
all hands on board ship, he was enabled to keep an instrument 
directed to any heavenly body notwithstanding the rolling or 
pitching of the vessel. The utility of this invention will be 
readily understood by those who have endeavoured to observe 
the occultation of a star or of Jupiter’s satellites on the deck 
of a sailing or steam vessel. With a similar apparatus he is 
able to register the degree and effects of all those motions, or 
to show any two of them combined. 
When Oersted perceived (in 1819) that a magnetic needle 
suspended freely could be turned to one side by the transmission 
of the electric fluid passing through a wire parallel and near it, 
no matter at what distance the battery was placed, the telegraph 
was virtually discovered. It took long years, however, to real- 
ize this invention; to find a fitting battery; a perfectly insu- 
lated wire ; a convenient code of signals. During the few years 
previous to the Exhibition of 1851 this science made immense 
progress. Not only were telegraphs then transmitting mes- 
sages, but actually printing them on ribbons of paper, and the 
electric current had even been used in recording the passage 
of a star across the wires of the transit-instrument ; thus throw- 
ing the ear out of employment altogether, and bringing the 
sense of touch into operation instead. Since that time the 
principal endeavour has been to simplify the alphabet, to obtain 
