XX XVI 
THK VOYAGE OF H.M.S. CHALLENGER. 
8ui a (-«>>sftil exploration of the deep sea had not been invented. Thanks to 
tiii rapid development of many branches of science, and the introduction of 
numerous instrumental improvements, thoroughly trustworthy results can 
now U* obtained in the most profound depths. 
In the Narrative of the Cruise of the Challenger the proceedings of 
the ship at sea,, the methods employed in deep-sea investigations, the 
general character of the observations, the excursions of the naturalists 
land the surveying operations of the naval officers, and the other events 
of the voyage have been duly chronicled. , In the Physical and Chemical 
Reports the continuous magnetic and meteorologic observations and the 
researches into the temperature, the specific gravity, and the chemical 
composition of sea-water, arc published with abundant illustration. In 
the extensive series of biological memoirs the new and rare organisms 
discovered b\ the Expedition are described and figured in great detail. 
A social volume lias been devoted to a discussion of the composition 
ami distribution of Deep-Sea Deposits. A very large part of the Challenger 
b«‘j" »rt thus consists of Special Memoirs, containing a great accumulation 
<»f r ; t4 ■ t . and many important generalisations in nearly all the branches 
of Oceanography. 
The area covered by the ocean is so vast, and the positions at which 
corn pb te sets of observations have been made are relatively so few, that it 
is hv'iueuth hazardous, from the information in our possession, to frame 
g<-ueiai statements with reference to the conditions prevailing over wide 
ar«-;ts of the deep sea. Even when such statements are prepared by 
those who have a competent knowledge of all the known observations 
oi the subject, they do not necessarily supply the information desired by 
student* engaged in the study of Oceanological problems. Particular 
observations are usually of more value to the scientific man engaged in 
a new research than any general statements. 
The Naturalist frequently wishes to know what observations exist with 
r . t.-rence t » tin* physical surroundings and biological associations of some 
animal in which he is interested. The general student or the chemist 
and geologist, desirous, it may he, of investigating the composition of sea- 
water or ol deep-sea deposits, often asks for similar information from a 
particular locality and depth, and he finds it difficult to gather any very 
