June 26, 1903.] 



SCIENCE. 



1011 



tions, seen stars well down toward the seventh 

 magnitude. 



The invisibility^ of stars of the seventh 

 magnitude or slightly fainter is due mainly 

 to the amount of light given by the back- 

 ground of the sky, even on the clearest nights 

 and in regions well removed from the Milky 

 Way (cf. papers by Professor Simon New- 

 comb, Astroph. Jour., December, 1901; Dr. S. 

 D. Townley, Pul. A. 8. P., No. 88, and G. J. 

 Burns, Astroph. Jour., October, 1902). At 

 Professor Newcomb's suggestion Director 

 Campbell has asked me to find my own limit 

 of naked-eye vision, having given as artificial 

 aids the direction of the star, and the Screen- 

 ing off of the light of the sky. 



Two blackened screens were attached to the 

 twelve-inch telescope at a distance apart of 

 1Y8 inches. The rear screen was pierced with 

 an aperture half an inch in diameter and that 

 at the object glass with one of one quarter 

 of an inch. These apertures were so aligned 

 that when a star was seen centrally through 

 them it would be found at the intersection of 

 the cross-wires of the three-inch finder. A 

 movement of two or three minutes of arc was 

 sufficient to carry the star out of the field 

 thus formed. 



The method of observation adopted was to 

 clamp the telescope at the proper declination 

 for the selected star. It was then swept slowly 

 in right ascension with the eye at the aper- 

 ture till the star was picked up. The posi- 

 tion of the star was then noted in the finder 

 and if not more than a minute or two of arc 

 from the intersection of the cross-wires the 

 observation was considered successful. Sev- 

 eral such trials were made on each star. 



Eleven stars were observed on three nights, 

 of which only the last could be called a very 

 clear night. The magnitudes of the stars 

 employed ranged from 6.42 to 8.5. It was 

 found that up to and including magnitude 

 8.0 the stars could be certainly seen in every 

 instance, though in no sense easy objects. 

 Stars of magnitudes 8.1, 8.2, 8.3 and 8.5 were 

 seen with great difficulty and with occasional 

 failures, generally when the eye was tired 



from the strain of searching for these very 

 faint objects. 



The contrast between the almost perfect 

 darkness of the object glass screen and the 

 sky immediately around it, as seen through 

 the rear aperture, was very marked. It seems 

 evident that for the observation of such faint 

 objects without telescopic aid the screening 

 off of the light of the sky is more important 

 than the concentration of the vision in a 

 definite direction as afforded by the use of 

 the apertures. Heber D. Curtis. 



Lick Observatoky, 

 April 22, 1903. 



4 MODIFICATION IN MEASURING CRANIAL CAPACITY. 



One of the most important, but at the same 

 time rather difficult and tiresome, manipula- 

 tions in anthropometry is the measuring of 

 cranial capacity. The importance of the 

 measurement lies mainly in that it gives us 

 the volume, as well as a fair basis for the cal- 

 culation of the weight, of the brain, both of 

 which data are very valuable in racial com- 

 parison, and, so far as most of the more 

 primitive races of people are concerned, are 

 quite impossible to be secured in any other 

 manner. 



It is plain that a procedure of such impor- 

 tance should be brought to the utmost possible 

 simplicity and perfection, and so regulated 

 that the capacity measurements could be 

 utilized with full safety and universally. This 

 sentiment was undoubtedly common to all 

 the practical workers in physical anthropol- 

 ogy up to the present day, and the results have 

 been an invention of many more or less related 

 methods for measuring cranial capacity, and 

 a gradual approach to an ultimate, generally 

 adoptable, procedure, under the circumstances 

 the nearest possible to perfection. It is in 

 connection with this very desirable, ultimate 

 method, the main points of which are already 

 well understood, that there is still a place for 

 some modification, and one such will be de- 

 scribed in this paper. In the first place, how- 

 ever, it is advisable to give a few explanatory 

 notes as to the various procedures in gen- 

 eral use. 



The many methods of measuring cranial 



