ON THE ADAPTATION OF SUSPENSION BRIDGES. 293 
Description of new species of Crangon, C. Pattersonii, in foregoing list :— 
Rostrum rounded, apex scarcely length of ocular peduncles; carapace with 
four (?) lines of spines ; abdomen smooéh, without sulcation, except in telson ; 
in other respects as Crangon spinosus. 
Additional List of Polyzoa. 
Crisia eburnea. 
Tubulipora patina. 
—— incurvata (n. sp.), Hincks. 
Diastopora obelia. 
Alecto granulata, 
—— major. 
— dichotoma-Lamouroux. A single spe- 
cimen of an Alecto has occurred, which 
seems identical with the fossil form de- 
scribed and figured by Lamouroux in his 
‘ Exposition Méthodique’ under the above 
name. 
Crisidia cornuta. 
Salicornaria farciminoides. 
Scrupellaria scruposa. 
Aitea anguina. 
Gemellaria loricata. 
Bugula flabellata. 
Flustra truncata. 
Membranipora pilosa. 
— Pouilletii (Audouin). 
— spinifera (Alder’s Catalogue). 
— solidula (n. sp.), Alder MS. Mr. Alder 
has previously obtained it from other local- 
ities. 
I have also met with the Asteroid 
Forbes. 
By the Rev. Tuomas Hincks. 
Membranipora simplex (n. sp.), Hincks. 
Lepralia Londsborovii. A very distinct and 
beautiful form is not uncommon amongst 
the dredgings, which | refer doubtfully to 
this species, of which very little is known. 
concinna. 
variolosa, 
—— nitida. 
—— Woodiana (n. sp.), Busk. This fine 
species has only been known hitherto as a 
Crag fossil. It will be described and 
figured by Mr. Busk in his forthcoming 
Monograph on the Polyzoa of the Crag. 
Peachii. 
ventricosa. 
eximia (n. sp.), Hincks. 
Cellepora armata (n. sp.), Hincks. I had 
already obtained this new species from the 
Dogger Bank. 
Eschara cervicornis, Busk. 
Arenella dilatata, Hincks. 
Zoophyte, Sarcodictyon catenata of 
Appendiz to Mr. Vianouss’ paper “ On the Adaptation of Suspension 
Bridges to sustain the passage of Railway Trains” (Rept. Brit. Assoc. 
1857). 
For calculations relating to Suspension Bridges, reduced to the simplest 
terms, and considering the curve of the chain as a parabola :— 
uit of length. 
superficies. . . . 
MOTMUE Ee Fem 0 Yi 
EIR Uo. +e dey 
”» 
” 
” 
1 foot. 
1 square foot. 
1 cubic foot. 
1 ton. 
. . . . 
. . . . 
x=half chord of parabolic curve of chain. 
y=versed sine of ditto . . . . . . ~ » pclear of supports. 
Ah=semi-parameter of the parabola . . . . 
N.B. fae by the properties of the parabola. 
w=minimum sectional area of the chain, exclusive of appendages. 
=appendages of the chain. (See explanations, a.) 
w+n=sectional area of chain, for calculating its weight and tension. 
u=weight of a cubic foot of iron. 
e=maximum weight admitted on chain. (See explanations, b.) 
