Inclined Plane when subjected to alternations of Temperature. 117 



The following were the measurements observed during the 

 month of May : — - 





Distance of the lower 











end of the lead from 









Date, 



zero of the vernier, in 



Descent in 



Descent in 



Descent in 



3858. 



inches. 



the day. 



the night. 



24 hours. 



Morning. | Evening. 



May 1. 



10-95 1 11-10 



15 







r 



The lead, overlapping the end of the board 





1 



by nearly a foot, was this evening drawn 





back to 0-77 









4. 



0-78 



106 



•28 



•03 



•31 



5. 



1-09 



1-21 



12 



•03 



•15 



6. 



1-24 



1-44 



•20 



•10 



•30 



7. 



1-54 



1-65 



11 



•02 



•13 



8. 



1-67 



1-88 



•21 



•00 



•21 



9. 



1-88 



1-93 



•05 



07 



12 



10. 



200 



219 



•19 



•00 



•19 



11. 



2-19 



225 



•06 



•05 



•11 



12. 



2-30 



2-33 



•03 



03 



•06 



13. 



2-36 



2-40 



•04 



•09 



•13 



14. 



249 



2-55 



•06 



•00 



•06 



15. 



2-55 



268 



•13 



•06 



•19 



16. 



2-74 



2-90 



•16 



•01 



•17 



17. 



291 



2-92 



•01 



03 



•04 



18. 



2-95 



3-08 



•13 



•08 



•21 



19. 



316 



350 



•34 



10 



•44 



20. 



3-60 



3-77 



•17 



•10 



•27 



21. 



3-87 



3-87 



•00 



•03 



•03 



22. 



390 



412 



•22 



•03 



•25 



23. 



4-15 



4-54 



•39 



•04 



•43 



24. 



4-58 



4-64 



•06 



•00 



•06 



25. 



4-64 



5-16 



•52 



•04 



•56 



26. 



5-20 



5-41 



•21 



•09 



•30 



27. 



5-50 



5-84 



•34 



•01 



•35 



28. 



5-85 



6-05 



•20 



•02 



•22 



29. 



6-07 



6-37 



•30 



•03 



•33 



30. 



6-40 



6-55 



•15 



•08 



•23 



31. 



6-63 



680 



•17 







The daily observations were given up on the 31st of May ; but 

 the positions of the lead were registered on the 19th, 22nd, 23rd, 

 24th, and 26th of the following month. The average daily de- 

 scents in successive months, measured in inches, were—- 



February. 



March. 



April. 



May. 



June. 



•1000 



•13806 



•16133 



•21500 



•21888 



To compare the actual descent on any day with that com- 

 puted by formula (22), it would be necessary to know, not the 

 extreme temperatures only of the lead on that day, but every 

 oscillation of temperature between those extremes; for every 



