34 The Ottawa Naturalist. [May 



yet, because of the inherent difficulty of proving anything by 

 the microscope, the limestones have been little studied. The 

 tendency has also been to neglect their macroscopic phenomena 

 in the field, although enough data has now been collected to 

 stimulate an interest in its application to causes and events. 

 It may soon be possible to classify sedimentary rocks according 

 to the sequence of formative events which they have undergone. 

 Such a classification is very much to be desired, as it will event- 

 ually give us 'a Natural History of the sedimentary rocks. In 

 this paper the attempt will be made to classify intraformational 

 glomerates with the above facts in mind. Thus, all intra- 

 formational glbmerates may be divided into two groups: 

 .4, those .whose present structure is contemporaneous with 

 their primary lithification ; and B, those whose present structure 

 is non-contemporaneous with their primary lithification. Again, 

 under class B, the present structures may be either previous or 

 subsequent to the primary lithification. We will examine the 

 classification more closely when we discuss the mode of origin 

 of each type. As stated before, field evidence strongly points 

 to the fact that it is impossible to explain all intraformational 

 glomerates by a single hypothesis. It has been suggested that 

 the rapidly growing amount of data concerning the occurrences of 

 such rocks makes it unwise to classify them all under the term 

 conglomerate. This statement will be appreciated fully by those 

 who have observed different occurrences in the field, or have 

 even read the descriptions by the authors who have studied 

 and described them. Laying aside for the moment the conclu- 

 sions reached by each investigator as to the origin of the par- 

 ticular intraformational glomerates in his area, we may at least 

 rely upon his attempt to describe what he has seen. Descrip- 

 tions of intraformational glomerates are so varied that one is 

 forced to the conclusion that the variations cannot all be the 

 resitlt of a single set of factors. The study of intraformational 

 glomerates is largely a study of the phenoclasts which bring 

 them so strikingly to the notice of the field geologist, and it is 

 upon the size, shape, structure (if present), and composition of 

 the phenoclasts that this present classification is largely made. 

 The arrangement of the phenoclasts may be heterogeneous, un- 

 sorted, parallel, banded, radiate or edgewise. The arrangement, 

 as well as the size, shape, structure and composition, of the pheno- 

 clasts is intimately connected with their origin and the depth 

 of water under which they were deposited, the strength of 

 tidal currents, if any, the topography of the sea floor, and 

 character of the sediments. The presence of organisms in the 

 slimy mud of the seas may also have proved a determining 

 factor in their evolution. 



