MappliKj Soils and Alkali. 25 



survey party. This traverse work should, however, Ije reduced to 

 a minimum. 



In carrying on traverse work or surveying of any description, the 

 methods used, where possible, should conform to well-established 

 methods, such as are given in Wilson's Topographic Surveying. 



In order to orient plane-table maps to true north and south, the 

 map on page 4, showing the lines of equal magnetic declination, is 

 given. The solid lines show equal declination and the dotted lines 

 show equal annual change. The lines are moving westward, so 

 that where the declination is east it decreases and where west it 

 increases annually. 



Samples for laboratory examination. — To avoid unnecessary work 

 and to prevent overcrowding of the laboratory force, it will be very 

 necessary to use care and judgment in the selection of samples for 

 mechanical or chemical examination. 



vSoil samples, as a rule, should not be collected until the party has 

 obtained a very thorough acquaintance with the type conditions; 

 then a description of the soil should be sent in upon Form 46. 

 This description should be of so general a nature that it will apply 

 to all samples collected from that soil in that district. Then, too, 

 this type description should be made of every soil type found in the 

 district, whether it is correlated with a soil occurring in other dis- 

 tricts or is a new type. 



After this general description has been sent in a limited number 

 of samples from not exceeding four places in each soil type, and 

 limited to one or tw o localities in the case of less important types, 

 should be collected and the individual samples described on Form 

 47, one card being used for each sample, whether it is of a soil or 

 subsoil, and each sample being designated by the local name adopted 

 for the type to which it belongs. 



It will be better to defer taking samples until the work has pro- 

 gressed sufficiently far to insure a thoroughly representative set of 

 samples. 



A separate card (Form 48) is provided for miscellaneous sam- 

 ples, such as marl, minerals, crusts, and plants, and in all cases 

 such samples should be fully described, and the kind and purpose 

 of the examination desired should be clearly stated. Often a 

 qualitative examination will answer if we know the purpose of the 



