THEIR ARRANGEMENT. 



139 



that the arrangement is of the quincuncial (f) order. It is further 

 noticeable, that the smaller number of parallel secondary spirals, 2, 

 agrees with the numerator of the fraction in this the f arrangement ; 

 and that this number added to that of the parallel secondary spirals 

 which wind in the opposite direction, viz. 3, gives the denominator 

 of the fraction. This holds good throughout ; so that we have only 

 to count the number of parallel secondary spirals in the two direc- 

 tions, and assume the smaller number as the numerator, and the sum 



Vertical Projection 

 of the -I Arrange- 

 ment. 



25 



21 



23 



22 



19 



21 



20 



IS 



16 



15 



li 



12 



11 



10 



Vertical Projection of the -A- 



Arrangement. 



27 



25 



24. 



23 



22 



21 



20 



19 



18 



17 



16 



15 



14 



13 



12 



11 



10 



209 



of this and the larger number as the denominator, of the fraction 

 which expresses the angular divergence sought. For this we must 



FIG 209. A cone of the White Tine, on which the numbers are laid clown, and the leading 

 higher secondary spirals are indicated : those with the common difference 8 are marked by 

 dotted lines ascending to the right ; two of the five that wind in the opposite direction are 

 also marlved with dotted lines : the set with the common difference 3, in one dix-ection, and 

 that with the common difference 2, in the other, are very mauiieot ia the cone. 



