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Sediments generally do not consist of particles of one size; sand is commonly mixed 

 with gravel or shells, and mud with sand. If the deposit consists almost entirely of one 

 constituent, only one noun should be used ; but if it consists of two or more constituents, 

 the name of the dominant constituent shall be placed first, followed by the other or 

 others as accessories. Thus, if a deposit of mud contains a considerable proportion 

 of sand, it should be recorded a,s M S (mud, sand) ; if a mud deposit contains shells, it 

 should be recorded as M Sh (mud, shells) . If a deposit consists of shells or coral so 

 broken and ground up that the general size of the particles corresponds to that of 

 sand, it should be recorded as sh S (shell sand) or co S (coral sand) ; in this case the 

 words shell and coral are descriptive and their abbreviations should begin with 

 lower-case letters. 



If a specimen contains specks of contrasting color or size, the abbreviation Sp, 

 immediately preceded by any descriptive terms, should follow the term designating the 

 type of deposit. 



3846. Nature of Bottom Materials 



The nature, such as soft, hard, sticky, stiff, or the size, as coarse, fine, etc., of the 

 materials is indicated by an adjective preceding the noun. The abbreviations of the 

 adjectives shall always begin with lower-case letters. The usage of most of the terms 

 is self-evident. 



When the consistency of the bottom material is determined hy feeling only, without 

 an examination, it shall be described by one of the adjectives, such as sticky, hard, or 

 soft, unaccompanied by a noun indicative of the material. Nouns shall be used only 

 when the bottom material has been visually examined. The use of the term rocky is 

 to be avoided in this respect; the term hard should be used instead in all cases where 

 applicable. The term rocky may be used when it is known that the bottom is bedrock 

 or consists of a material larger than gravel but no specimen can be secured for examina- 

 tion. The term broken should be used as a modifying term to describe the condition 

 of shells or coral. (See also 783.) 



3847. Colors of Bottom Samples 



The color of the specimen should always be noted while it is wet, as the color of 

 some sediments is different when dry. The terms dark and light should never be used 

 alone; they are intended for use m qualifymg the intensity of a given color, as for 

 example, light gray, dark green. Where the color of the specimen is best described 

 by a combination of two colors, it may be done by hyphenating the two colors, the 

 predominant one being placed last, as yellow-green. 



Unfortunately, color perception differe considerably in individuals so that uni- 

 formity is difficult to achieve. For best results two or more individuals should examine 

 and agree as to the color of the specimen. ■ 



3848. Geographic Distribution of Deposits 



Close to shore and on the continental shelf the marine deposits generally consist 

 of sands, gravels, and muds, with which are frequently mixed the remains of animals 

 and plants. These are the sediments which are defined in 3844. They are usually 

 found in depths of less than 100 fathoms, and within an average distance of 75 miles 

 from land. 



465382—44 21 



