104 REPORT—1857. 
La somme >) est de la forme 
pete Bts _(ys—Bos)—e 
y+s (gts) 
Cette quantité, toute réduction faite, devient 
(y=aye Pr iil <8 
yooltl (a+B—yt1)tst} ¥ 
En Ja substituant dans l’expression précédente de r(2*), et en remar- 
Dae 
quant que (—1)*= +1, il en résulte la formule (a). 
Pourque la formule (a) ne soit pas illusoire, il faut que a+6—y+, sill 
est entier négatif, ne sort pas en valeur absolue moindre que —@, ou moindre 
que e—6é si par hasard cette derniére quantité est entiére négative moindre 
que —a en valeur absolue. 
La formule (4) se déduit de (a) si l’on identifie F4 i Bae \ avec 
1 gts a+B—yt+l, € 
: ees = en posant a=a', B=', e—d=0', a+ B—y+1l=el, e=y’; et 
que l’on applique la formule (a) aux lettres a’, f!, &e. 
La formule (d) se deduit de (a) en posant 
e—o=a', B=d', a=f', 
cer a+B—y+ ] =; 
! os 
appliquant la formule (a) 4 F rene et transformant le facteur en de- 
hors de F. ; 
Report on the Marine Zoology of Strangford Lough, County Down, 
and corresponding part of the Irish Channel. By G. Dicxiz, W.D., 
Professor of Natural History, Queen’s College, Belfast. 
Tue entrance to Strangford Lough is less than two miles in breadth; it gra- 
dually becomes narrower, forming a channel half a mile broad with a length 
of about three miles. The tidal current in this channel is estimated as 
having a velocity of nine miles per hour; as a consequence of such pecu- 
liarities, we find near Portaferry a depth of twenty-nine to thirty-five fathoms 
in the centre of the channel, and a gradual slope upwards from mid-channel 
to both shores. The bottom, in the deepest part, consists of rock with large 
and small stones interspersed; near the shore we find a mixture of small 
stones and gravel, and in the small bays sand or mud, or both intermixed. 
The wider expansion of the Lough itself presents very much the same 
characteristics of bottom, with this difference, that the proportion of hard 
material is very much less, a large part consisting of mud. These pecu- 
liarities give rise to corresponding differences in the distribution of animal 
life, as the following facts testify :— 
The fauna of parts of Strangford Lough has been examined by the late 
