1871.] 



as indicated by the Alpine-Tunnel Observations, 



483 



work, the smoke and foul air were drawn out of the tunnel by a ventilator 

 near the roof. 



The following tabular statement, adapted from that published by Signor 

 Giordano, will show the nature of the observations for temperature made 

 in the course of the works from the Italian side : — 



No. of 

 observa- 

 tions. 



12. 



13. 

 14. 



15. 



Distance in 

 feet from S. 

 entrance. 



1312 

 1640 



3281 



3675 

 6562 



8202 

 9266 

 9843 

 13124 

 16404 

 19686 



21156 



21858 

 22967 



22993 



TemperatuiN 



Air. 



o ^ 



50-9* 

 50-9 



59-5 



640 



68-5 

 73-4 

 764 

 80-2 



86-2 



77-0 



Hock or 

 water. 



O 



51-8' 

 57-6 



62-6 



62-6 



67- 



68- 



730 

 74-5 

 81-5 

 84-0 



85-1 



82-4 

 80-6 



77-9 



Observations. 



Small spring. 



Boring from heading 24 feet 

 from wall of tunnel 



Boring of 16 feet from heading 

 28' from wall 



Small spring 



Boring of 10' from heading 

 21*' from wall 



Small spring 



Ditto 



Boring of tbat like No. 5 



Ditto 



Ditto , 



Boring of 10' in a recess 13' 

 from wall near tbe point 

 wbere the excavation of the 

 tunnel was suspended till 

 the communication was 

 opened with the French side. 



Boring of 7' under the culmi- 

 nating point of the moun 

 tain with 5280 feet of rock 

 overhead. Small heading 7' 

 from wall 



Small spring. 



Boring of 7' into wall of small 

 heading 



Small spring. Initial tempera- 

 ture probably rather higher. 



Depth in 

 feet. 



1500 

 •1700 

 3000 



4500 



5280 

 4750 



It thus appears that the observed difference of temperature of the rock 

 between the distance of 1640 feet from the entrance and the distance of 

 21,156 feet is 27°'5 F. The difference of depth beneath the surface in 

 that distance is about 4600 feet. It is thought possible that the real 

 difference may be somewhat less, as the increased temperature of the air in 

 the heading, owing to the number of men employed and the frequent 

 blasting, may have influenced the result in some measure ; and it is perhaps 

 safer to estimate the total increment at something less than 26^° F. 



In the absence of observations that can be absolutely depended on, we 

 may perhaps assume the true maximum temperature of the rock to be 84°. 

 The part of the tunnel having this permanent temperature is 1295 m or 

 4250 feet above the sea, and the corresponding point of the surface is 

 9530 feet above the sea, showing a difference of 5280 feet. A careful esti- 



2q2 



