222 Analyses of Books. (Sept. 
that when stimuli (alcohol, opium, tobacco,) are applied to the 
brain or spinal marrow, the action of the heart is greatly increased ; 
and that when the brain or spinal marrow is destroyed at once by 
crushing them, the action of the heart is destroyed or impeded. 
7. Experiments to ascertain the Influence of the Spinal Marrow 
on the Action of the Heart in Fishes. By Mr. William Clift.— 
From these experiments it appears that the heart of a carp continues 
to beat for several hours after the pericardium is laid open; that if 
the fish be left in the water, this action ceases much sooner than if 
the fish be allowed to remain quiet in the open air; that the spinal 
marrow may be destroyed, and the brain removed, without injuring 
the action of the heart; but that this action is somewhat injured by 
suddenly destroying the brain. 
8. Some Experiments and Observations on the Colours used in 
Painting ly the Ancients. By Sir Humphry Davy, LL.D. F.R.S. 
—The author, while in Italy, had an opportunity of examining 
some pigments found in the baths of Titus, and some dug up from 
Pompeii. He made experiments also upon the fresco paintings in 
the baths of Titus. The following are the facts which he ascer- 
tained:—1. The ved colours employed in these paintings were red 
lead, vermilion, and iron ochre. 2. The yellows were yellow ochre, 
in some cases mixed with chalk, in others with red lead. The 
ancients likewise employed orpiment and massicot as yellow paints. 
3. The llue was a pounded glass, composed of soda, silica, lime, 
and oxide of copper. Indigo was likewise employed by the ancients, 
and they employed cobalt to make blue glass, 4. The greens were 
compounds containing copper; sometimes the carbonate mixed with 
chalk, sometimes with the blue glass. In some cases they consisted 
of the green earth of Verona. Verdigris was likewise used by the 
ancients. 5. The purple colour found in the baths of Titus was 
either an animal or vegetable substance, perhaps the colouring 
matter of the mrex combined with alumina. 6. The Llasks were 
carbonaceous matter; the browns, ochres often containing manga- 
nese. 7. The whites were chalk or clay. White lead was known 
likewise to the ancient painters. 
9. On the Laws which regulate the Polarization of Light by 
Reflection from Transparent Bodies. By Dr. Brewster.—This 
paper may be considered as a treatise on the subject. The author 
ascertained by experiment that the index of refraction is the tangent 
of the angle of polarization. From this law he shows how all the 
phenomena may be deduced, and the result of all the experiments 
determined beforehand. But‘from the great conciseness of the 
paper, and the mathematical dress in which it has been put, it is 
out of our power to convey to our readers an intelligent abridg- 
ment of it. 
a 
Il. A Treatise on the Economy of Fuel and Management of 
Heat, especially as it relates to eating and Drying by means of 
