Mechanical Science. 433 
1 paper pulp, 1 glue, 3 white bole earth, 1 linseed oil; a 
beautiful elastic sheet. 
When these plates or slates were steeped in water for four 
months they were found not to alter at all in weight; and when 
exposed to a violent heat for five minutes, they were hardly 
altered in form, and were converted into black and very hard 
plates.— Tech. Rep. ii. 421. 
9. Damp Walls.—The following method is recommended to 
prevent the effect of damp walls upon paper in rooms. Line 
the damp part of the wall with sheet-lead, rolled very thin, and 
fastened up with small copper nails. It may be immediately 
covered with paper. The lead is not to be thicker than that 
which lines tea-chests. 
10. Improvement in Trusses. —We understand that Mr. Coles, 
of Thames-street, has effected a considerable improvement in 
the construction of trusses, by which the pressure upon the ring 
is not merely equalized, but which adjusts itself, without incon- 
venience to the wearer, to the different attitudes in which the 
body may be placed. 
11. Result of the Experiments made by order of the Board of 
Longitude, for the Determination of the Velocity of Sound in the 
Atmosphere. Drawn up by M. Arago.—The observations were 
made by a commission, consisting of MM. Humboldt, Gay- 
Lussac, Bouvard, Prony, Mathieu, Arago, and Rieussec. 
They have deduced from the mean of two days’ experiments, 
on the report of cannons, measured as to their times of being 
heard, by excellent chronometers of M. Breguet, that at 10° C., 
the velocity of sound per second is 173.01 toises = 337.2 
metres = 1]06.32 English feet, estimating the length of the 
metre to be 39.37079 English inches, as determined by Captain 
Kater.—Ann. de Chim. et de Phys, xx. 211. 
Il. CuHEmicaL SCIENCE. 
1. Ona New Class of Compounds of Sulphur. By Dr. Zeise, 
of Copenhagen.—If a certain quantity of sulphuret of carbon 
be poured into an alcoholic solution of one of the alkalies, a 
neutral liquid is obtained, in consequence of the formation of a 
new acid, which neutralizes the alkali. If potash has been 
used, the salt may be obtained either by refrigeration, evapora- 
tion, or precipitation, by sulphuric ether. It contains no car- 
bonic acid, or sulphuretted hydrogen, but an acid, which is in 
the same relation to sulphuret of carbon that hydrocyanic acid 
is to cyanogen. Its compounds have been called hydrocarbo- 
sulphates. 
Vou, XIV. 2F 
