99 
Putting tan 6, tan ¢, tan y respectively for the right-hand 
sides of the preceding equations, we obtain 
tan (BAP — 4 BAC) = tan} BAC tan (47 — 8), 
tan (CBP —4CBA) =tan $CBA tan (47 — 9), 
tan (ACP — $ACB) = tan $ACB tan (4 — wW). 
Whence, knowing the segments BD, CD, CH, AE, AF, BF, 
the position of P can be found. 
Any five of the segments of the sides of ABC may be taken 
for the elements of the crystal. Tor five of the segments being 
known, the remaining segment is given by the equation 
sin BD sin CH sin AF =sin CD sin AX sin BF. 
On the Association of Potton Sand Fossils with those of 
the Farringdon Gravels in a phosphatic deposit at 
Upware on the Cam; with an account of the Super- 
position of the Beds, and the significance of the 
Affinities of the Fossils. By Mr Harry SzeExey, 
ABSTRACT. 
Ix 1860 the author had traced the Galt by Swaffham fen, 
west of Wicken into Soham Mere; fossils were then collected 
and placed in the Woodwardian Museum. But though the beds 
over the Kimeridge clay and under the Galt are represented in 
Dr Fitton’s section through Upware, they do not appear to have 
been seen again until the pits were opened for digging nodules 
of phosphate of lime last year. These have yielded about 120 
species of fossils, chiefly mollusca and spunges, with a number 
of vertebrates. As a whole they recall beds in the same posi- 
tion in the north of Germany ; in part they resemble with un- 
expected closeness the fauna of the Farringdon gravels; while 
