CHAP. IT. | THE CRUISES OF THE ‘ PORCUPINE’ D3) 
ing dissimilarity in Animal Life, and to trace this climatic 
dissimilarity to its source; as well as to carry down the like 
survey to depths much greater than have been yet explored by 
the Dredge. ; 
“This, it is believed, can be accomplished without difficulty 
(unless the weather should prove extraordinarily unpropitious) 
by the employment of a suitable vessel, provided with the 
requisite appliances, between the middle of May and the middle 
of September. The Ship should be of sufficient size to furnish 
a Crew of which each ‘watch’ could carry on the work con- 
tinuously without undue fatigue, so as to take the fullest advan- 
tage of calm weather and long summer days; and should also 
provide adequate accommodation for the study of the specimens 
when freshly obtained, which should be one of the primary 
objects of the Expedition. As there would be no occasion to 
extend the Survey to a greater distance than (at the most) 400 
miles from land, no difficulty would be experienced in obtaining 
the supplies necessary for such a four months’ cruise, by running 
from time to time to the port that might be nearest. Thus, 
supposing that the Ship took its departure from Cork or Galway, 
and proceeded first to the channel between the British Isles and 
Rockall Bank, where depths of from 1,000 to 1,300 fathoms are 
known to exist, the Dredgings and Temperature-Soundings could 
be proceeded with in a northerly direction, until it would be 
convenient to make Stornoway. Taking a fresh departure from 
that port, the exploration might then be carried on over the area 
to the N.W. of the Hebrides, in which the more moderate 
depths (from 500 to 600 fathoms) would afford greater facility for 
the detailed survey of that part of the Ocean-bottom on which a 
Cretaceous deposit is in progress—the Fauna of this area having 
been shown by the ‘ Lightning’ researches to present features of 
most especial interest, while the careful study of the deposit 
may be expected to elucidate many phenomena as yet unex- 
plained which are presented by the ancient Chalk Formation. A 
month or six weeks would probably be required for this part of 
the Survey, at the end of which time the vessel might again run 
to Stornoway for supplies. The area to the N. and N.E. of 
