548 



Observations on Pure lee and Snow. 



[June 10, 



of crystallised calcium chloride and two parts of snow, which yielded 

 a temperature of —39° F. 



The vessel containing this mixture was itself further surrounded 

 by another freezing mixture of a constant temperature of —4° F., and 

 this arrangement was found to work admirably in maintaining a pro- 

 longed and constant low temperature. An alcohol thermometer was ' 

 employed for taking the internal temperature of the mass of ice, sub- 

 stituting a little alcohol at the bottom of the protecting tube instead 

 of mercury. The results are contained in Table IT. 



It will be noticed that the coefficients become less as the tempera- 

 ture is reduced. 



Table II.— Dilatation of pure Ice between —35° F. and +32° F. 







Column 1. 



Column 2. 



Column 3. 







Transversely 

 measured at 



Longitudi- 

 nally- 

 measured at 

 32° F. 

 become 



Linear expansion. 







32° F. 

 become 



Transverse. 



Longi- 

 tudinal. 



1000 part 



33 

 5? 

 33 

 33 



s at + 16° F.. . 

 zero F. . . 

 -21° F. . 

 -30° F. . 

 -35° F. . 



1000- 654 

 1001 -103 

 1001 -533 



1001- 712 

 1001 -871 



1000 -657 



1 in 1529 

 1 „ 906 

 1 „ 652 

 1 „ 584 

 1 „ 534 



1 in 1522 



Linear coefficient for 1° between + 16° F. and + 32° F. = '000040876. 



„ +16 „ =0-000028042. 

 „ „ -21 „ =0-000020484. 



-30 „ -21 „ =0-000019744. 



Set III. — Relative Hardness or Penetrability of Ice at Temperatures 

 letween -35° F. and +32° F. 



The observations were periodically taken during the gradual in- 

 crease in the temperature of the ice cylinder from —35° F. to +32° F. 

 A polished steel rod, 16 inches long by 0*292 inch diameter, blunt 

 at the end, was allowed to penetrate the ice under the influence of a 

 weight of 181-J lbs. resting on its summit. A suitable apparatus was 

 arranged to carry out this set of observations, which is roughly de- 

 lineated on the sketch, fig. 1. 



The relative depths to which the steel rod penetrated the ice under 

 the varied conditions of temperature (which were frequently ascer- 

 tained by thermometers) compared with the penetrability at —35° F. 

 afforded approximate indications of the relative hardness or penetra- 

 bility of the pure ice under the conditions of experimentation. The 



