. The prospector's field-book and guide in the search for and the easy determination of ores and other useful minerals. ecting points which can be readilyfound upon the map, and, if possible, lie at the sameheight, which can be readily effected without essen-tial error with the assistance of an aneroid barome-ter by taking observations in rapid succession. Thepoints of same height, for instance, 1 and 2, givethe strike of the stratum for a greater distance. By connecting the outcrops of oil a by a line AA,and again determining in the latter several pointsof the same height, for instance, 3, 4
. The prospector's field-book and guide in the search for and the easy determination of ores and other useful minerals. ecting points which can be readilyfound upon the map, and, if possible, lie at the sameheight, which can be readily effected without essen-tial error with the assistance of an aneroid barome-ter by taking observations in rapid succession. Thepoints of same height, for instance, 1 and 2, givethe strike of the stratum for a greater distance. By connecting the outcrops of oil a by a line AA,and again determining in the latter several pointsof the same height, for instance, 3, 4 and 5, thegeneral strike is again obtained. If the latter runsparallel with the general strike of the characteristicstratum S, previously traced, one is justified in in-ferring a bed-like occurrence of oil, even if the con- PETROLEUM, OZOCERITE, ASPHALT, PEAT. 259 strued dip of the outcrop line of oil correspondswith the observed local dip of the strata. In these investigations it is presupposed that theoil is recognized as exuding from the solid rock, anerror regarding the outcrop of it being, therefore, Fig. excluded. Such an error may, however, occur whenthe outcrop is covered with loose masses of earthand rock, to the base of which the oil exudingabove flows down hidden, and escapes further belowby some accidental cause. A vein-like occurrence of oil will not show the 260 PROSPECTOR S FIELD-BOOK AND GUIDE. above-mentioned conformities with the characteristicconcordant strata. Such an occurrence presupposesa fissure, which is generally connected with a throwof the strata. This is most frequently establishedby the fact that a characteristic stratum suddenlyends and does not reappear in its natural continua-tion, but either to the right or left, or higher orlower. If two or more such points of disturbance Fig. 62.
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