20 Improvements in Physical Science [Jan, 
the action of that power. The different experiments on adhesion 
made by Brook Taylor, Morveau, and Achard, are well known, 
together with the defects of these experiments, pointed out long 
ago by Dutour. The subject still requires a good deal of experi- 
mental elucidation. Mr. Ruhland (Schweigger’s Journal, ii, 146) 
has lately made a number of very curious experiments on adhesion, 
which deserve to be generally known. I shall give a short abstract 
of them here, leaving out his explanations, which do not appear to 
me to throw much light upon the subject. 
He found a weight of 46 grains necessary to separate a watch 
glass from the surface of mercury. On heating the watch glass, 
58 grains were requisite to separate the two surfaces. When the 
wateh glass and mercury were allowed to acquire the same tempe- 
rature, the same weight (or rather less) as at first, was sufficient to 
separate the two surfaces. ‘The same experiment succeeded when. 
marble was substituted for the watch glass. 
Mr. Ruhland found, as indeed was known before, that when the 
smooth surfaces were rubbed against each other, their adhesion 
_ was very sensibly increased. I suspect in these cases the agency of 
electricity: the two surfaces probably acquire different states’ of 
excitement. 
He took a small glass plate and made it adhere to the surface of 
a little mercury placed in a watch glass. The weight necessary to 
separate the two surfaces was three grains. The mercury was now 
brought in contact with a little nitric acid ; of course an effer- 
vescence took place, and some nitrate of mercury was formed. 
The weight now necessary to separate the two surfaces was seven 
grains. The same experiment was repeated various ways, always 
with a similar result. Mr. Ruhland supposes that a thin film of 
nitrate of mercury gets between the metal and the glass. 
The following table exhibits the weights which were found 
necessary to separate equal surfaces of the bodies, stated in thie 
table, from different liquids. 
Water, twice distilled. 
Zine ~ sis sale w TF BiB Tallow .......0+ 76 gris. 
WY arg ieidet andi 79 Lead suet wides wifRn on 
Sealing wax.... 70° Marble .. eve IF 
Glass . bis wee J5'S Sulphur ........ SO 
Oil of Almonds. ; 
Marble ... 50 grs. | Wax ...... 56 grs. | Tallow .... 54 grs, 
Alcohol, diluted with thrice its Weight of Water. : 
Marble .... 45 grs.. | Wax...... 50 grs. | Tallow .... 49grs. 
Twenty Grains concentrated Nitric Acid in two Ounces of Water. 
Glaks... +0: c040 OF OTN. War”. po eteen ns Mt tae 
Tead evesvseocves 67 Tallow ecoeerecere 69. 
Sulphur ......6. 65 
