486 GEOTECTONIC (STRUCTURAL) GEOLOGY. [Boox IV. 
ripple-marks, rain-prints, or sun-cracks (Fig. 200); so that more than 
one kind of evidence may be gleaned from a locality to show that it 
was sometimes laid bare of water. 
These more striking indications of littoral conditions being 
comparatively infrequent, the geologist must usually content him- 
self with tracing the gravelly detritus, which suggests, if it does not 

Fic, 200,—Foorrrints AND SUN-CRACKS, HILDBURGHAUSEN, Saxony (SICKLER). 
always prove, proximity to some former line of shore. Sucha section 
for instance as that depicted in Fig. 201 may often be found, where 
lower strata (a) having been tilted, raised into land, and worn away, 
have yielded materials for a coarse littoral boulder-bed (0), over which, 
as it was carried down into deeper and clearer water, hmestone 
eventually accumulated. Beds of conglomerate, especially where, 
a 

Fic, 201.—Secrion or A Bracu or warty Mesozoic AGE, Near Citron, Barstou(B.) 
a, Carboniferous limestone; b, dolomitic conglomerate—a mass of boulders and angular — 
fragments of « (some of them almost two tons in weight), passing up into finer 
conglomerate c, with sandstone and marl, and thence into dolomitice limestone d. 
as in this example, they accompany an unconformability in the 
stratification, are of much .servige in tracing the limits of ancient 
seas and lakes (see Part’X,):. 2 6 Ss fe 
Gas-spurts.—The éuirfaces of some strata, usually of a dark 
colour and containing orpani¢ matter, .may be observed to be 
raised into little .keaps of :vatigue indeGaits shapes, not like the 


