746 T. C. BROWN OOLITES AND OOLITIC TEXTURE 



to the eye, like the cob or ovary of a herring, or some smaller fishes, but for 

 the most part, the particles seem somewhat less, and not so uniform. . . . 

 "Where these grains touch each other, they are so firmly united or settled 

 together, that they seldom part without breaking a hole in one or th' other of 

 them, such as a, a, a, 1), c, c, &c. Some of which fractions, as a, a, a, a, where 

 the touch has been but light, break no more than the outer crust, or first shell 

 of the stone, which is of white color, a little dash'd with brownish yellow, 

 and is very thin, like the shell of an egg; and I have seen some of those 

 grains perfectly resemble some kind of eggs, both in color and shape: But 

 where the union of the contiguous granules has been more firm, there the 

 divulsion has made a greater chasm, as at h, &, h, in so much that I have ob- 

 served some of them quite broken in two, as at c, c, c, which has discovered 

 to me a further resemblance they have to eggs, they having the appearance 

 of a white and yelk, by two differing substances that envelope and. encompass 

 each other" (loc. cit., page 93). 



See plate 26, figure 1, for a reproduction of Hooke's figure. 

 Even at this earl}^ date the question of origin received attention, for 

 Hooke continues: 



"I must not here omit to take notice, that in this body there is not a vege- 

 tative faculty that should so contrive this structure for any peculiar use of 

 vegetation or growth, whereas in other instances of vegetable porous bodies, 

 there is an anima, or forma informans, that does contrive ail the structure 

 and mechanisms of the constituting body, to make them subservient and use- 

 ful to the great Work or Function they are to perform" (ibid., page 95). 



After this pioneer description and observation on oolitic rocks little 

 attention was given to them until about half a century ago. As geolog- 

 ical knowledge advanced and as geological observations were extended, it 

 became known that oolitic rocks were abundant and wide-spread at many- 

 geological horizons. The name "oolite" was even used as a formation 

 name in England for certain portions of the Jurassic system. The actual 

 formation of oolites, or of structures differing from these only in size, 

 and hence called pisolites, was observed in such surroundings as the 

 Carlsbad springs, while the oolitic texture was found to be characteristic 

 of rocks other than limestones, because it occurred in iron ores (both 

 hematite and siderite) and in siliceous rocks. 



A.S the importance of oolites and the oolitic texture became apparent, 

 attention .was directed to their origin, and from the very beginning two 

 widely different views were advocated by various authors. As early as 

 1851 De La Beche remarked that in shallow bays or tidal seas in warm 

 climates, where evaporation is rapid, the sea- water would lose a part of its 

 carbonic acid and thereby be forced to deposit a portion of the calcium 

 carbonate which it held in solution. He writes :* 



* Sir Henry T. De La Beche : The Geological Observer, pp. 122-123. London, 1851. 



