Geological Society. 513 



sels in the lungs to be sedative or relaxing, and ascribe to a dimi- 

 nished action of these vessels the apparently increased efficiency of 

 the right side of the heart when oxygen is applied, we suppose the 

 oxygen to produce the very opposite effect to that which has always 

 been observed when it or any other stimulus has taken effect on any 

 individual artery. 



The only mode in which it appears possible to escape from these 

 difficulties is to suppose that the stimulus given by the oxygen to 

 the flowing blood through the lungs, is a stimulus to that movement 

 which is independent of any contraction of the solids containing 

 the blood. This conclusion is in perfect accordance with the ob- 

 servations of Haller on the derivation of blood, perceptible under 

 the microscope, towards any part where an opening is made in a 

 vessel, and air admitted into contact with the blood, because he 

 gives satisfactory reasons for thinking that this derivation is not 

 owing to contraction of the vessels ; it is also in accordance with 

 observations on some of the lowest tribes of animals, and on vege- 

 tables, where currents in fluids are observed in connexion with the 

 act of respiration, but no movement of solids has been detected; and 

 even, as Dr. Alison thinks, with the observations of Purkinje and 

 others, on currents connected with the respiratory organs in animals 

 much higher in the scale, because although these last currents have 

 been ascribed by most authors to vibrations of ciliae, which are seen 

 to accompany them in various instances, it seems very doubtful 

 whether they can be adequately explained without supposing a 

 "jeu d 'attraction et repulsion" to be commenced in these instances, 

 as well as in the respiration of the lowest tribes. 



[To be continued.] 



GEOLOGICAL SOCIETY. 



June 10. — A paper was first read, entitled " Note on theTrappean 

 Rocks associated with the (New) Red Sandstone of Devonshire :" by 

 Henry T. De la Beche, For. Sec. G.S. 



The author remarks, that while trappean rocks are not found among 

 the (new) red sandstone series of Somersetshire and the more north- 

 ern portions of Devonshire, the southern portions of the latter county 

 afford many examples of the association of trappean rocks with the 

 lower parts of this series, particularly near Tiverton, Thorverton, Sil- 

 verton, Kellerton Park, Crediton, and Exeter. 



When hastily viewed, the trappean rocks might be mistaken for 

 masses of igneous matter which have been intruded, in a state of fu- 

 sion, among the beds of red sandstone. A more detailed examination 

 of the various facts connected with their mode of occurrence leads, 

 however, in the opinion of the author, to the inference that they have 

 been produced by volcanic action during the formation of the lower 

 parts of the (new) red sandstone series ; in fact, that the trappean rocks 

 in question are the remains of melted rock, either ejected from, or re- 

 tained within the pipes of, volcanoes which were in a state of activity 



