30 



That the laws which regulate their effects on the muscles of volun- 

 tary and involuntary motion are different. 



That both mechanical and chemical stimuli applied to any part of 

 the nervous system tend to increase the action of the heart. 



That neither mechanical nor chemical stimuli applied excite the 

 muscles of voluntary motion, unless they are applied near the origin 

 of the spinal marrow. 



That mechanical stimuli have more effect than chemical on volun- 

 tary muscles, but the reverse with respect to those of involuntary 

 motion. 



That all stimuli continue to affect the heart long after they have 

 failed to excite the muscles of voluntary motion. 



That the motions thus excited in voluntary muscles are irregular, 

 but those of the heart more regular. 



That the former occur chiefly at the first moment of application, 

 but those of the latter as long as the stimulus is applied. 



That the former depend on intensity of the stimulus, the latter on 

 the extent of surface to which it is applied. 



That the power of the blood-vessels, like that of the heart, is in- 

 dependent of the nervous system, though they may be influenced 

 through that system, as the heart is. 



That the actions thus excited are regular, as those of the heart, 

 and that their power, like that of the heart, may be destroyed 

 through the nervous system. 



On the Fire-damp of Coal Mines, and on Methods of lighting the Mines 

 so as to prevent its Explosion. By Sir H. Davy, LL.D. F.R.S. 

 V.P.R.I. Read November 9, 1815. [Phil. Trans. 1816, p. 1.] 



The great sources of fire-damp in coal mines are blowers or fissures 

 from which currents of this inflammable gas issue in considerable 

 quantities and for a long series of years ; but there is also a certain 

 quantity produced by the workings. The author was informed by 

 Mr. Hodgson, that if a cask be filled with a quantity of recently 

 pounded coal, and a small aperture be made in it, inflammable gas 

 will issue from the aperture. 



In several specimens of fire-damp which the author has analysed, 

 the inflammable part was the same in all ; in some instances mixed 

 with a small quantity of common air, in others with azote and car- 

 bonic acid. The purest contained only T Vth of atmospheric air. 

 One measure of this gas required nearly two measures of oxygen for 

 its combustion, and formed nearly one measure of carbonic acid. 



Sulphur heated in this gas decomposed it, forming sulphuretted 

 hydrogen, and precipitating charcoal. 



This gas, when mixed with chlorine, does not combine by exposure 

 to light ; so that it appears to contain neither olefiant gas nor hydro- 

 gen, and seems to be the same as the inflammable gas of marshes, 

 or pure carburetted hydrogen. 



