‘ 
Mechanical Science. 153 
rometric pressure on the opposite sides of the previously existing 
partition of rock than probably existed. , 
6. Nautical Eye-tube.—A trial has been made on board the Clio 
among the Orkneys, and in the Moray Frith by Mr. Adams, of 
the performance of his eye-tube to the telescope of a sextant for 
taking altitudes when the horizon is invisible. In making the ob- 
servations the horizon was always screened from the instrument, 
and under these circumstances after rejecting a few observations 
the mean difference of 199 altitudes of the sun, moon, and stars, 
taken by the eye-tube, from those taken at the same time in the . 
ordinary way by the officers of the Clio, and corrected for dip, 
amounted to only 1’10”. The altitudes taken by the eye-tube 
are not affected by any dip or depression of the horizon. Consider- 
able care and practice is required in the use of the instrument, but 
that attained, the latitude, the time at the ship, and consequently the 
longitude may all be determined by it when the horizon is invisi- 
ble. By means of it also either the large or the pocket sextant 
may be employed on shore as a substitute for the theodolite, upon 
making the necessary allowance for the parallax of the instrument 
in the name of index, error, which oa becoming sensible, must vary 
inversely with the distances of the reflected terrestrial objects.— 
N. M. Mag. xii. 16. 
7. Leghorn Straw Plait.—The Dublin Society having offered 
premiums for the best imitations of Leghorn plait, awarded three 
prizes to successful candidates. Not less than twenty-four speci- 
mens were exhibited from widely remote parts of Ireland. The 
finest specimen was made from avena flavescens, or yellow grass, 
by Miss Collins of Plattin, near Drogheda. The second was 
made of cynosurus crystatus, or crested dog’s tail, by Miss Grimley 
of Kiltinon, near Newton Mount Kennedy. The third of agrestis 
vulgaris, or common bent grass, by Miss Campbell of Lon- 
donderry. 
IJ. Cuemican Science. 
1. On Fulminating Silver and Mercury.—The following results 
are collected from a memoire on these substances, by Dr. Just 
Liebeg, which has appeared in the Annales de Chim. xxiv. 294. 
The fulminating silver was obtained by dissolving about 60 grains 
of fine silver ia half an ounce of nitric acid, spec. grav. 1,52, add- 
ing two ounces of alcohol of spec. grav. .85, and heating slowly 
in a flask until ebullition commenced ; in a short time, white crys- 
talline flocculi appeared, the vessel was removed from the source 
of heat, and left to cool. The ebullition continued some time, and 
