Prof. W. A. Norton on Donati’s Comet. 79 
Interazillaries—In a line with the radial, and between the two oppo- 
site arm pieces, is one to three quite small pentagonal interaxillary pieces ; 
sometimes two yet smaller pieces occur. 
nal pieces, one; small, quadrangular; one is superimposed on the 
subradial, followed by three pieces of like form and size, and similarly 
TO 
ARr. X.— Theoretical Determination of the Dimensions of Donati’s 
Comet; by Prof. W. A. Norton. ‘ 
: I HAVE recently undertaken to bring the theory developed in 
Previous number of this Journal,* in an article entitled ‘“ Dy- 
Prag Condition of the Head of a Comet,” to the test of numer- 
dim Computations, by determining, by calculation, the theoretical 
“a. of the great Comet of 1858. e more im 
for 's may be briefly stated; the complete discussion is reserved 
at subsequent number of the Journal. 
: # Vol. xxvii, [2], 86. 
