In many aquatic larvae we find that all the spiracles are closed up, or become functionless, except a pair at the hinder end which are associated with some arrangement - such as the valvular flaps of the gnat larva or the telescopic " tail " of the drone-fly larva - for piercing the surface film and drawing periodical supplies of atmospheric air.
A protracted controversy with Johann Hevelius, in which Hooke urged the advantages of telescopic over plain sights, brought him little but discredit.
In other factories the cells are arranged in lines and are charged from the slicer by suitable telescopic pipes or other convenient means.
This was done in 1612 by Christoph Scheiner, who fully described his method of solar observation in the Rosa Ursina (1630), demonstrating very clearly and practically the advantages and disadvantages of using the camera, without a lens, with a single convex lens, and with a telescopic combination of convex object-glass and concave enlarging lens, the last arrangement being mounted with an adjustable screen or tablet on an equatorial stand.
Also several optical problems relating to lenses of various forms and their combinations for telescopic projection, rules for finding foci, &c. He does not, however, mention the camera obscura as an instrument in use, but in John Harris's Lexicon Technicum (1704) we find that the camera obscura with the arrangement called the "scioptric ball," and known as scioptricks, was on sale in London, and after this must have been in common use as a sketching instrument or as a show.
The smallest and most numerous class are the telescopic meteors invisible to the naked eye.
It is computed that twenty millions of meteors enter the atmosphere every day and would be visible to unassisted vision in the absence of sunlight, moonlight and clouds, while if telescopic meteors are included the number will be increased twentyfold.
The shaft is lined with a cylinder of wrought iron, within which a tubular chamber, provided with doors above and below, known as an P g air-lock, is fitted by a telescopic joint, which is tightly sinkin packed so as to close the top of the shaft air-tight.
Made until the introduction of Scott's telescopic sight.
Other advantages are those common to all telescopic sights.
9.-Scott'S Telescopic Sight.
The introduction of trunnionless guns recoiling axially through a fixed cradle enabled sights to be attached to the non-recoil parts of the mounting, so that the necessity of removing a delicate telescopic sight every round disappeared, and Q?'
Continuous laying and telescopic sights became possible.
On the 1st of October 1847 she discovered a telescopic comet (seen by De Vico Oct.
- a, Microcodon clavus, showing corona, lateral antennae and jointed foot; b, Rhinops vitrea, corona from below, showing proboscidiform extension containing eyes; c, Philodina megalotrocha; d, head of Rotifer macroceros, postero-ventral view, showing lobes of corona, and antero-dorsal median antenna, telescopic with setae; e, Rotifer (Actinurus) neptunius, showing head with retracted corona, and protruded dorsal proboscis bearing median antenna, and telescopic foot with toes and spurs; f.
Bdelloidaceae; foot with two toes and accessory spurs or a simple perforated disk; body telescopic at either end, with an antero-dorsal proboscis ending in a ciliate cup and bearing the proximal antenna; corona usually bilobed, very wheel-like.
At the same time, on land, the new necessities imposed on field artillery by the growing use of covered positions led to the development of scissors-telescopes (see Rangefinders) and panorama-telescopic sights (see Sights), in which the optical system was arranged with the tube of the telescope vertical and the object-glass and eyepiece systems at right angles to the axis of the tube.
1) the upper prism is supported above the telescopic system on a flat strip of metal which can be slid through side supports on the body of the periscope.
A steel telescopic mast and upper and lower optical systems which are attached to it.
The telescopic mast is carried in trunnions on the carriage, and travels closed and in a horizontal position.
The telescopic mast consists of 8 tubes.
To re- duce resistance, these cupolas were made telescopic in the French submarines "Gymnote "and the " Gustave Zede, " but the arrangement proved unsatisfactory.
When the larvae are disturbed the similarity is produced with startling suddenness by the telescopic contraction of the anterior segments in such a manner as to suggest a triangular, pointed head with two large dorsal eyes.
Six months later, the indefatigable astronomer started for Danzig to set at rest a dispute of long standing between Hooke and Hevelius as to the respective merits of plain or telescopic sights; and towards the end of 1680 he proceeded on a continental tour.
This led to his invention of the micrometer and his application of telescopic sights to astronomical instruments of precision (see Micrometer).
The subsequent history of the development of the art of manufacturing glass disks for telescopic objectives will be found in the article Glass: § Optical.
This yields a very much smaller field of view, but it is very valuable for viewing feeble telescopic objects.
Far within the limit to which telescopic vision can extend binary systems are now being found by the spectroscope.
These systems appear as a connecting link between short-period variable stars on the one hand and telescopic double stars on the other.
The great cluster in Hercules (Messier 13), on the other hand, requires the highest telescopic power for its complete resolution into stars.
Actually we know that the intrinsic brightness varies very greatly, so that each increase of telescopic power not The table, which is based on over 130,000 stars, shows that along the galactic circle the stars are scattered nearly three times more thickly than at the north and south poles of the Galaxy.