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POPULAR SCIENCE REVIEW. 
A Glycerine Barometer. — Mr. James Jordan communicates to the Royal 
Society the details of this instrument. Many attempts, as he states, have, 
been made from time to time to construct barometers with fluids of lower 
density than mercury, with the view of increasing the range of oscillation. 
He expresses the belief that such instruments may show the character of 
more minute vibrations of atmospheric pressure at storm stations. Many 
have been made with water, notably one in 1830 at the Royal Society, by 
Prof. Daniell. These, however, are vitiated by the effects of change of 
temperature on the water vapour in the vacuum, which marks changes of 
pressure. Glycerine, from its high boiling-point, has a very low tension of 
vapour at ordinary temperatures, and a very small coefficient of absolute 
expansion. The specific gravity of the purest glycerine is 1*26, less than ^-th 
that of mercury. The mean height of the column is 27 ft. at the sea level; 
a variation of -A- in. i n the height of the mercurial column is equal to more 
than an inch in glycerine. As it is very hygrometric its surface is covered by 
a shallow layer of heavy petroleum oil. 
The tube is formed of ordinary composition metal pipe of f in. internal 
diameter. To this is cemented at the top a glass tube 4 ft. long, with inside 
diameter of 1 in. The upper end is formed into an open cap fitted with an 
indiar ubber stopper. Two scales, one on either side, read off the height, one 
being divided into inches and tenths of absolute measure, the other into 
equivalent values of mercury. 
The cistern is cylindrical, of copper tinned inside, 5 in. deep and 10 in. 
diameter, with a cover and small orifice covered with cotton wool to keep 
out dust. Glycerine, coloured red by aniline, was heated to 100° Fahr. and 
placed in the cistern ; by means of an air-pump connected with the top of 
the tube the level was raised 323-571 inches, or within *3 of the Kew standard. 
A plug was then screwed in below to support the column, the tube was 
filled at the top with glycerine, and the stopper inserted. Some precautions 
were adopted to allow air to escape, and the column was finally allowed to 
take its own position. It will be regularly observed by the Superintendent 
of the Observatory. 
Accidental double Refraction forms the subject of a communication to the 
Annales de Chimie et de Physique by M. Mace de Lepinay. He distinguishes 
four kinds : 1. By pressure or tension, discovered by Brewster. 2. Lamellar 
polarization, due to cubic crystalline structure. 3. Results of unequal tem- 
perature or chilling. 4. Double refraction from high electrical tension, as 
discovered by Kerr. The first (1) is simply proportional to the force employed, 
starting with a certain value, and leads to some remarkable results ; for 
instance, quartz cut perpendicularly and compressed gives lemniscate curves, 
thus becoming biaxial for the time. Under the second (2) come the experi- 
ments of Seebeck in 1812 and Brewster in 1814, which have been revived 
with practical purpose of late by M. de Bastie in his toughened glass. These 
are clearly due to excessive surface tension. The writer of the memoir goes 
into long and careful experiments as to ( a .) the distribution of stress in 
rectangular plates ; (b.) the verification of Wertheim’s law of wave-lengths ; 
(c.) the variations of ordinary and extraordinary indices in various points 
of rectangular plates. The paper itself extends to ninety pages, and con- 
tains, besides the direct objects of the inquiry, some valuable collateral 
