C. D. Fawcett 
421 
by Herbert Thompson at 1173 and b}^ C. D. Fawcett (mean of three determi- 
nations) at 1222. Of course some of this difference may be due, as we have 
suggested, to the gradual elimination of more of the desert sand, but the bulk of 
it was undoubtedly personal equation. Either C. D. Fawcett packed less tightly 
in the measuring glass or more tightly in the skull, than H. Thompson did ; 
either way the result is that there is a difference in the determinations which may 
run up to 20 or 30 cm.'', and much the same holds, if either of our estimates are 
compared with those of the far-more practised Professor Thane. We look upon the 
capacity-determination as subject to large personal equation, and we do not see 
how to correct it. As we got practically identical results with seed or sand, so we 
believe different observers watching each other's methodb would rapidly learn to 
do the same, but whether such accordant results would give the true capacity of 
the skull, we are more inclined to doubt. 
Herbert Thompson measured 39 male and 55 female Naqada crania. C. D. 
Fawcett measured 69 males and 98 females. Further, Dr Alice Lee has esti- 
mated the mean capacity of these crania from the values of length, breadth and 
height measured by C. D. Fawcett*. She has also determined from the Leipzig 
collection of Theban mummy skulls the mean capacity of 201 males and 
96 femalesf. The following are the results : 
TABLE 11 
Mean Capacity. 
Material 
Sex 
No. 
Mean Capacity 
Naqada (H. Thompson) 
s 
39 
1339 
? 
55 
1243 
Naqada (C. D. Fawcett) 
s 
69 
1.387 
)) )i 
? 
98 
1279 
Naqada (Dr Lee's Formula) 
6 
69 
1377 
" '.' 
? 
98 
1255 
Ancient Egyjitians 
201 
1390 
)) )> 
? 
96 
1254 
Now allowing for the difference of the sample it is clear that there must be a 
large personal equation element in the differences between H. Thompson and 
C. D. Fawcett, upwards of 30 to 40 cm.' Roughly weighting his and her </ 
series at 6 and 8, his and her % series at 7 and 10 respectively, we find : 
Mean capacity for Naqada </ crania = 1366, 
„ „ „ „ $ crania = 1264. 
* Phil. Trans. Vol. 196, pp. 225—264. 
t Loc. cit. p. 246. A longer series of Egyptian mummies with much the same results is given by 
Pearson ; Chances of Death, Vol. i. p. 339. 
