8 



quicker upwards than the snow-line, and from August to January 

 quicker downwards. The snow-line therefore in the first period 

 coincides with isothermals warmer than 0° C. ; in July it is even 

 at +5° C. The snow-line, in the usual sense, that is to say its 

 highest limits in summer, is, at the mean temperature of the year^ 

 -4° C. 



13. Over large masses of snow and glaciers there is remarked, 

 particularly on fine days, a descending current of air (glacier-v/ind), 

 which has a great influence on the general depression of temperature 

 near the limits of snow. 



14. The absolute extremes of cold on single days are at the lower 

 stations sometimes so great, that they are comparatively but little 

 surpassed by those on the higher points. But the differences be- 

 tween the higher and lower part are much [greater if we consider 

 the maxima of heat. The absolute maxima seem scarcely ever to 

 exceed 5" or 6° C. on the highest summits of the Alps. On all days 

 the decrease of temperature is greater at the time of the maximum 

 than at the minimum. 



15. Compared therefore to the temperature of high latitudes, the 

 summits of the Alps correspond nearly to 70° N. Lat. But the cli- 

 mate of the highest elevations on the Alps is much less severe than 

 that of Northern Asia, and is more constant than that of Polar 

 America. Their minima of winter are much surpassed by nearly all 

 stations in northern latitudes ; but the maxima of summer are 

 colder than those of nearly all points on high latitudes at little ele- 

 vation above the sea. 



A .paper was also in part read, entitled " On the Exogenous Pro- 

 cesses of the Vertebrae." By Professor Owen, F.R.S. &c. Received 

 November 8, 18.50. 



The Society then adjourned over the Christmas holidays, to meet 

 again on the 9th of January. 1851. 



January 9, 1851. 

 Lieut.-Col. SABINE, R.A, V.P. and Treasurer in the Chair. 



The reading of Prof. Owen's paper " On the Exogenous Processes 

 of Vertebrae" was resumed and concluded. 



The author commences by a definition of these as contradistin- 

 guished from the autogenous parts or ' elements' of a vertebra, and 

 exemplifies them by instances from Human and Comparative Ana- 

 tomy, which show the necessity of a distinct substantive term for 

 each of such parts and processes. The terms proposed are as 

 follows : — 



