96 



Tlir tit'lli nvciauf. !'•• rays, is I'dinid in live Idealities, iliree iif wliieli are lieluw 

 1,00(1 i'eet. ami the iiigliest is at l.l'dO. 



Tile sixth average, of 20 rays, varies Iroiii 'A7'> to 'l.loU feet; twn nf theiii are 

 at an elevation of less tlian 1,000 feet. 



This grouping does not show any nniforni variation \\itli the altitude. It 

 may he emphasized tiiat the lowest average is not found lielow 1.47") feet, that 

 only one of the s^'Ven having an averag<' of Hi I'ays is found l)elow 1,000 feet, and 

 that but one of the eiiiht having an average of 17 rays is found below l,(l00 feet. 

 From the last imt threi' speeimens are known. It may be further emphasized that 

 three of the hve loealities having an avei-age of lU rays are found below 1,000 feet, 

 and that two of the three having an average of "JO rays are found below 1,000 feet. 

 Generally liie lower locality has the larger number of rays, to which tiiere are 

 several notable exceptions. Lake Washington aud Snake IJiver at Payette. These 

 facts can be jiresented in curves for groU])S of localities. 



Taking the specimens from the diHerent groups of localities we ol>tain the 

 tidlowiuii' : 



Eli'valion, Feet. 



X umber of 

 Lot-alitios. 



\ umber of 

 Specimens. 



Extent of 

 Variation. 



(ieneval 

 AveraRe of 

 Anal Rays. 



1 to 750 



1.078 lo ixm 



2.001 to 3,100 

 5,000 t(. 



IS>.I 



2:!4 



38S 



10 



Whether we "finsider the nuudiei- of localities ha\ing a hiuh a\ei-a<;c of rays 

 or whether we consider tiie averagi's of all the specimens from a similar liori/.on, 

 we find that the largest num!)er of rays is found in the lower hoi-i/.ou. I'^irther- 

 more, the extent of vaiialion for the I s'.l >pecimens from 1 to 7">0 feet is gi'eater 

 than tile variation f<u- "J-'U and SSS specimens of the higlu'r horizons. Tlu' \aria- 

 tion for these tlii-ee horizons is given in tiu' three curvi's of tigui'e .'>. 



In the .above we have cnnsidei-cd the localities regardless of the system to 

 which they belong. Lake .NVashiuuioii and the Newaucum and Skookniiu'huck 

 rivers iielong to separate short wati'r courses. Kliminating these aud considi-i ing 

 the localities of the I- razor aud of the ('(dumbia systems separately we get the 

 conditions described for the l-"razer system ai)ove and for the Columbia system the 

 following— arranging tlu' localities in the order of elevation : 



