only an examination of the oompoF5ition, texture, chemistry etc 

 01 existing sedinents, but also the restoration, fro-a these ** 

 characters, and from the factors in the environment that compel the 

 deposicion of one kind of sediment and not of another, of the con- 

 ditions as to depth of water, temperature, activity of circulation, 

 distance irom land, topography of bottom, etc., under which the old 

 sediments aocui-nulated. For this he needs to know which classes of 

 seaiments are so sensitive to environmental factors that they are 

 deposited oniy under special combination of these, and which classes 

 are eitner less sensitive or are limited by only a single factor, 

 e.g., -Gemperaturs: tne rocks derived from the first group have a 

 limite^, tnose from the second a much more general distribution. The 

 organic secim.entB may be expected to prove especially instructive in 

 txiis connec-Gion because certain of them seem so closelv bound to par- 

 ticular envirormients that when their requirements are once comprehen- 

 dea it will be possible to translate the old organic sediments i'^to 

 terms of tne physical and chemical conditions under which they were 

 laia down. Since sediments of different sorts are laid down in 

 seauence, cnanging as the environment changes (e.g., if the sea floor 

 rises or sinks), study of the old sediments should also give us the 

 sequences of such changes in the old seas. 



It is, therefore, no exaggeration to name the study of modern 

 suomarme sediments (as has been done) a geologic necessity, for only 

 by this meane can geologists hope to understand how the different 

 classes of sediments, now solidified into rock, were actually accui'iu- 

 lated, ano. still more important, what chemical changes they have under 

 gone on tne floor of the sea, since that time. Neither the studv of 

 modern sediments alone, nor of their ancient prototypes now rs-ore- 

 sented by tne sandstones, chalks, and limestones can tell the whole 

 story :_ the two must be examined hand in hand. Systematic dredr-ine 

 and lao oratory studies of the material so far gathered from the ^-Stto«- 

 ot the sea are lively to throw a flood of light on such outstanding 

 problems as the origin of the various kinds of limestone, dolomites, 

 petroleu:-) deposits (Page 11), and of the valuable deposits of potash 

 and otner sa.lt s. 



The transformations that chemical changes in the im.pregnatins 

 water may nave caused in the limy sediments"'on the floor of the ocean 

 deserve particular attention, because we know that while the old 

 sedimentary limestone and shale rocks were laid doiTn under wate.", and 

 uxiaer conditions comparable to those existing todav, thev differ 

 greaoly from the muds and oozes that are now bein? deposited. I- 

 «'^> °°r®^^°'' new studies on the hardening (diagenesis) of marine 

 sediments are urgently needed to explain the origin of the old 



ol'^^'iot-^'' '"^''i^ T^ ?-'® e^'^'fe-^'s crast. The formation of phosohatic 

 concretions and of glauconite, also needs study, for its bearing on 

 the origin of pnosphate and potash rocks. 



The importance of the problem of iron in the deep-sea sedir.erts 

 il°ll^'''^^Ji^'^ ^® remember that most of the iron ores of todav v-ere 

 al..ost^cerbainly laid down under the sea over a wide range of " 



-f?^?"-o-.?!?°'^^- -^-?o§^°^~ -'^°^' ^^^■^^^ °^'^i^ White's report to the 

 o,T'? o-^ ^^^"""^ oi 1933 ''..e do not know how they were deposited in 

 sucn enormous amounts, and in their present relations to other 

 minerals and rocks. I^iat were the water, the biologic, the bottom, 



