486 Mr. Legros Clark on the Mechanism of Respiration. [May 25, 



The absence of observations from the French side appears more and more 

 unfortunate as we advance in the investigation, and renders the general 

 result by no means so satisfactory as it would otherwise be. It would appear, 

 indeed, that distance from the surface alone is not by any means the only 

 cause of increased temperature in the case of a lofty mountain mass ; but 

 how far this is due to imperfect observation, the want of properly sheltered 

 instruments, and local causes connected with the progress of the works, it 

 is not easy to say. There may also, no doubt, be some difference arising 

 from the imperfect modes of estimating the mean annual temperature and 

 the temperature and depth of the stratum of permanent temperature. But 

 although all these are subject to a certain amount of correction, there is 

 enough general accordance of the observations to show that the conclusions 

 indicated must be accepted. Considering that we are in the heart of the 

 great mountain axis of Europe, the conditions are simple and favourable. 

 There is little or no permanent snow or ice on either side, and no glaciers : 

 one slope (that to the south) is at first rapid, and then in steps ; the 

 other slope is very regular. The tunnel is of great length, and most 

 parts of it of enormous depths below the surface, compared with any other 

 depths that have been reached ; and it has been mentioned already that the 

 geological conditions are unusually simple, especially in the southern end 

 of the tunnel, to which all the observations are confined. No case has ever 

 before occurred in which there was so much opportunity of making syste- 

 matic and trustworthy observations on the subject of the internal tempera- 

 ture of the earth ; but as it is not unlikely that the successful comple- 

 tion of the tunnel under the Mont Frejus may be followed- by other similar 

 undertakings in other parts of the Alps, the experience here gained may at 

 any rate be turned to account to secure better and more systematic work 

 elsewhere. 



Note. — Since the above memoir was written, the author has been in 

 correspondence with Prof. Sismonda of Turin, and has obtained permission 

 to repeat the observations recorded, to make corresponding observations in 

 the bore-holes at the French end of the tunnel, and to obtain observations 

 of the temperature at the surface. These observations will be made with 

 instruments provided by the British Association Committee for investigating 

 the rate of increase of underground temperature, and will be conducted by 

 the author, who hopes to visit the tunnel during the present summer. 



II. " Some Remarks on the Mechanism of Respiration." By F. 

 Le Gros Clark, F.R.C.S., Professor of Anatomy and Surgery 

 at the Royal College of Surgeons. Communicated by Prof. P. 

 M. Duncan, F.R.S. Received April 18, 1871. 



(Abstract.) 



The author commences his paper by narrating some experiments on 

 recently slaughtered animals, in the course of which the remarkable tension 



