Mat 25, 1906.] 



SCIENCE. 



815 



H„ 13.18; N,, 2.21; total, 100.05. The shales 

 burn readily with a long yellow flame and 

 slight bituminous odor. 



Thin sections of the light chocolate shales 

 show them to contain minute, flattened, gen- 

 erally oval and discoid, translucent bodies of 

 a brilliant lemon-yellow color, and highly 

 refractive, the refringence, as determined by 

 r. E. Wright, being 1.619. These yellow 

 bodies, varying from 8 to 62 microns in hori- 

 zontal diameter and 5 to 20 microns in ver- 

 tical, usually thinly lenticular and irregularly 

 rounded at the edges but often nearly oval, 

 are, in vertical section, seen to lie horizontally 

 matted with other sediments, and crystals of 

 later formation, precisely like the matting of 

 forest leaves beneath the winter snow. While 

 varying greatly in size, they accommodate 

 themselves topographically when overlapping 

 or surmounting the coarser rock material, and 

 seem to preserve their individuality even when 

 apparently in contact. They are incredibly 

 numerous, constituting over 90 per cent, of 

 the rock mass in the richest layers. 



Under proper microscopical manipulation, 

 the larger of the yellow bodies appear to in- 

 clude a number of horizontally oval figures, 

 characterized by an extremely narrow and 

 usually obscure marginal ring, and a small, 

 roundish, or slightly irregular, denser, and 

 often darker-colored mass near the center. 

 These figures, averaging about eight microns 

 in length and five microns in width, are sus- 

 pended in the translucent yellow bodies, in 

 which they are similarly compressed horizon- 

 tally. They are regarded as probably corre- 

 sponding to the contours of collapsed and flat- 

 tened unicellular plants, the outer ring repre- 

 senting the cell boundary, the inner, denser 

 portion the residual contents of the cell, whose 

 original gelosic envelope is preserved as the 

 bright, lemon-colored, environing mass. The 

 smallest yellow bodies appear to have con- 

 tained a single oval, the larger ones, several. 

 The yellow bodies are, therefore, interpreted 

 as the fossil remains of microscopical, uni- 

 cellular, gelosic algse, apparently comparable 

 to the living Protococcales. They appear to 

 have been somewhat enriched in bitumen after 



the cessation of bacterial disintegration, 

 which, in the buff shales, does not seem to 

 have progressed sufficiently to form a notice- 

 able fundamental jelly. 



The black oil shale differs from the light 

 chocolate and buff rock chiefly by the deeper 

 color, probably due to greater humification and 

 bituminization of the gelosic bodies, and, more 

 particularly, by the suspension of the latter in 

 a dark brown ground mass or fundamental 

 jelly. The details of the oval figures and the 

 included, denser, small, central masses are 

 much more strongly defined and generally 

 more deeply colored. The slightly smaller 

 size of the yellow bodies in the black shale is 

 regarded as due either to greater shrinkage 

 under the influence of the bitumen, or to 

 more extensive bacterial reduction. The dark 

 brown ground mass appears to consist of a 

 fundamental jelly, largely filled with minute 

 mineral matter and granulose frag-mental 

 debris or wreckage due to destructive bacterial 

 action on the gelosic bodies, many of which, 

 like the small fragments of larger forms of as- 

 sociated algag, are greatly corroded. Many of 

 the gelosic bodies were doubtless completely de- 

 composed. To this bacterial work on the or- 

 ganisms is due, in the judgment of the author, 

 the essential character of the somewhat humi- 

 fied, fundamental jelly itself, to which there 

 has probably been accession of attracted bi- 

 tumen. The more extended bacterial action 

 seen in the black shales is interpreted as ante- 

 cedent and causally related to the greater 

 bituminization of the organic matter rather 

 than as merely incidental or accidental. 



The oil shales owe their volatile hydrocar- 

 bon contents either directly or indirectly to 

 the fossilized gelosic residues of microscopical 

 organisms regarded as algse, which locally 

 compose over 90 per cent, of the sedimentary 

 material. These pelagic or floating algse fell 

 in prolonged showers in quiet or protected 

 areas where the water was presumably some- 

 what charged with tannic or humic solutions 

 conducive to the arrest of anaerobic bacterial 

 decomposition. Possibly the bacterial action 

 was arrested by its own products. The orig- 

 inal deposits were doubtless several times as 

 thick as those now remaining, since it is prob- 



