Diagram I. 
MR. J. H. GRAY ON A METHOD OF DETERMINING 

er 

lela 

orig he 
LL 




Z 
e 


























BEERS ae | 































ie \ 
HEHE SSS 
ST SN 
Ree oe ean 
| eee Na 


eepnubpnias prinehesy 

eA 

erasers 
reed 
PACTS 4S 
ay 



(SERA aS aa ee eae 

Time in Half-Minutes. 
24 26 28 30 52 34 36 38 40 42 44 46 478 50 52 54 56 58 60 62 Gt 66 
22 
10 l2 14 16 18 20 
4 6 6. 
2 
