Chronometers. 189 
a sufficient distance, a very simple and efficacious mechani- 
cal apparatus 1s used to destroy its poise, causing it to fall im- 
mediately, but remaining still attached by the line and moor- 
ed by a small anchor, with which it is equipped.”? One end 
of the rope being thus conveyed to the shore, and fixed by 
this small anchor, some one of the hands is enabled to get 
on shore and render assistance to others. ‘The importance 
of the object is sufficient to recommend every expedient for 
its accomplishment. Capt. D. is particular to recommend 
certain proportions for the construction of the kite. The 
canvass or holland Is extended upon two spars whose lengths 
are to each other as 2 to 3, the cross-piece intersecting the 
standard so that the upper section of the standard shall be to 
the lower section as 1 to 2. At two points on the standard, 
about 4 of its length from the head and the same from the 
bottom, two lines are attached, the upper about 2} of the 
length of the kite, and the lower 2 of its length, which com- 
bined form the belly-band ; and to their point of junction is 
attached the line which is to retain the kite. The tail may’ 
be 5 or 6 times the length of the kite, and its weight must b: 
proportionate to the wind. : 
To effect the descent of the kite, the end of the line re- 
tained in the vessel is slipped through an apparatus, called 
the messenger, which, having a sail attached to it, is immedi- 
ately taken up by the wind along the line towards the kite. 
This messenger by driving out a wedge which is essen- 
tial for the proper poise of the kite, so transfers the centre 
of suspension, that a rapid descent of the kite and apparatus 
attached is a necessary consequence. Some experiments 
made with this instrament have given Capt. D. much confi- 
dence in the success of his invention.—Trans. Soe. Arts, 
Man. & Com. 
22, Chronometers.—Mr. Harvey, F. R.S. . has lately 
discovered that the density cf the medium in which a chronom- 
eter 1s placed has a sensible influence on its rate, in most cases 
producing an acceleration when the density is diminished or 
a retardation when the density is increased. In a few time- 
keepers he has found the reverse to take place, viz. a de- 
crease of rate from diminished density, and an increase from 
iicreased density ; but the former appears to be the most 
general effect. Mr. Harvey has proved this to be the case 
by an extensive course of experiments, in which he has 
Vor. X-—No. 1. 24 
