III. SURVEYING. 769 



3034. Pocket Compass, for bearings of objects, &c., an in- 

 strument for travellers. Made by O. S. Bishop. 



Capt. C. George, R.N. 



A combination of the ordinary compass and the dipping needle. The 

 advantage aimed at is, that it will act at or near the magnetic pole when the 

 ordinary compass ceases to be of any use. 



3032. Universal Tripod Stand, an instrument for travellers. 

 Made by H. Porter. Capt. C. George, R.N. 



May be used for five instruments, viz.: 

 Sextant (for Lunars). 

 Telescope. 

 Barometer. 

 Prismatic compass. 

 Artificial horizon. 



3139. Spectacles for Divers, for use in water. 



Francis Gallon, F.R.S. 



When we look down into still clear water we see all objects in it with per- 

 fect distinctness, but the moment that the open eyes touch the water all 

 distinctness of vision ceases. The convex surface of the eyeball has indented 

 the plane surface of the water with a plano-concave lens, and, if we desire to 

 restore distinctness of vision, we must use convex glasses of sufficient power, 

 when immersed in water, to neutralise this effect. A double convex flint 

 glass, each of whose surfaces has a radius of about half an inch, is therefore 

 required. By means of the glasses exhibited it is possible to read the smallest 

 type under water, with perfect ease. The principle of these glasses was 

 described in a memoir read before the British Association in 1865. 



3140. Ground Tongs for Sea Soundings; invented by 

 Francis Hopfgartner, Austrian Imperial and Royal Naval Officer 

 of the line. Lieut. Hopfgartner. 



A hole is bored lengthways through .the centre of an ordinary plummet. 

 In this hole is inserted a movable metal rail, at the lower end of which there 

 are attached two scoops or spoons, opening and closing by means of a hinge 

 or link. At the upper end there are two movable bows which are joined to 

 the ladles by small chains. If the plumb-lead is suspended to these hook-like 

 bows by means of two short auxiliary lines, the scoops are opened and the 

 apparatus is then ready to be let down into the water. On reaching the 

 ground the bows will fall back, dropping the auxiliary lines, the weight of 

 the lead presses the scoops into the ground, and by pulling up the main plumb- 

 line, which is now acting directly on the metal rail, the scoops are closed and 

 drawn into the hole of the lead so far as to be securely closed. 



3141. Ground Tongs for Sea Soundings, with disengag- 

 ing weight ; invented by Francis Hopfgartner, Austrian Imperial 

 and Royal Naval Officer of the Line. Lieut. Hopfgartner. 



Two scoops or spoons, intended for securing specimens of the sea bottom, 

 are opened and closed like a pair of tongs by means of two levers. A peculiar 

 metal cover, in which the ladles will fit, secures the closure of the same. At 

 the upper ends of the two limbs of the tongs there are two hook-like mov- 

 able bows, on which the lead is placed, which , on the apparatus being let 

 down into the water, keeps the scoops in an open position. On reaching the 

 ground the bows will drop back, the weight (stone or a ball) will fall off, and 

 the metal cover will encase the scoops, and keep them closed while the appara- 

 tus is being pulled up. 



40075. 3 C 



