ON THE ABSOLUTE MEASUREMENT OF HARDNESS. 227 
able accuracy is further increased. Values of ¢ obtained in this way 
for different plates and different lenses of the same material and radius 
in each case show larger differences than the foregoing analysis has 
made probable. Hence it is reasonable to suppose that the different 
samples really differ as to elasticity, although the differences and the 
probable errors are surprisingly small. 
Glass I, values of q. 
p=1 =o | A + e=12 + p=4 tL 
| 
| = a | | : 7 = a = Sa |] vr eae 
| AGHA ees | Moor Passe coe 122/1 2.7 || 39.4 0.2 
Pe ae eee | 455 | SORE Rites 110.6 | lig 1 38.3 0.3 
BOD eee | Ted Ee ceesee 115.7 | 1.3 || 38.7 0.3 
a See 456) es deed 147.7 | 26! 40.0! 0.1 
TOT Fe eee | CD ee | | 
| | | 
[VON Be ere eee 7M UR ae | 
ODM es ceesesars | AVON |e eee | | 
| AU Sa ae ee tm: | 
| Mean results ...... 1 463 4|/ 116.5 | 1.6 39.1 0.25 | 
| | | | 
Glass IT, values of q. 
| FF ioe | 
p= a p=) 4 P10: + | poe 
202. 6 1.9 118.9 1.0 58.5 1.5 36.7 0.9 
196, 3 Scania aLIIAG 3.0 57.2 1.3 37.3 0.4 
190. 6 Bulge LDS Bal sea ers: SA 39.0 1.6 
| | | 
195.7 27 || ee: 2.6 59.7 | 1.5 39.2 0.7 
196. 3 1.9 111.3 1.5 || 59.3 PRL a Beg al vee | 
SGA VA Se 5 Shee, 116. 0 2.4 || BOR IE Mek Eph LE SA CE Se a he 
Do. pean Pee yee neree 112.7 3.8 59.6 Die pice ee hak Y wiley em Bs. 
St eee 117.1 | 0.7 55. 3 | | co ROI, Fe ak ae 
ee 81) es | 120.0 0.9 56. 0 11S Eek el 
—_— ——- —_———_— | —— 
195. 4 iy) 114.9 0.7 58.3 0.4 || 38.3 0.4 | 
| 
Glass IIT, values of q. 
Me | + 
p=4 p=12. | p=3 
4 ; 
160i) {set eh.2 2. Mie Pay on Ps a 22.0 0.1 
yf a) Sees } Sie Peeps « ae 21.7 0.0 
BW We ek I BORG so Neer 21.7 0.1 
Ce Se oe | Roady Wok seed. 21.6 0.1 
ROrd efit & (eer ee | ang 0.1 
[an ES | eRe a | Pee 259 0.1 
162.5 Ly 53.0 0.2 21.85 0.05 | 
| 
| 
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