Reviews — Petroleum and Gas Resources of Canada. 37 



unfortunate results. It would have been preferable to include more 

 of the Canadian element in the authorship, for certainly in the first 

 volume the writers appear only at their ease when citing examples 

 from the United States, but as a general treatise on petroleum 

 vol. i will probably find a much wider circle of readers than 

 those interested in Canadian oil-fields. In it are collected what 

 is really a series of essays on petroleum problems, some of them but 

 mediocre, a dull restatement of well-trodden ground, but others 

 distinctly fresh and well-balanced, with clear concise wording 

 where descriptive, and full of suggestive ideas where theoretical. 

 It would probably have been of advantage to omit most of the first 

 chapter, for to summarize the world's oil occurrences in thirty 

 pages, country by country, is to attempt the impossible and to 

 involve the bewildered student in a labyrinth of dead place-names. 



Chapter ii contains much useful physical and chemical data, while 

 under the heading " Geological Occurrence of Petroleum and Natural 

 Gas ", chapter iv, there is a clear and short account of the various 

 theories of the production of natural hydrocarbons, in which the 

 author safely joins both sides of the warring camps of the upholders 

 of organic origin. But the remarks on oil migration do not break 

 any fresh ground, and here unfortunately the need is most lamentable. 

 There comes a time in the history of all theories when a few adverse 

 storms are necessary to unsettle the fallacies which take root 

 so easily and to orient ideas to fresh facts. It is a pity that the 

 current ideas of oil migration have lived so long in the belt of calms, 

 for, strange as it may seem when considering the importance of the 

 subject, we do not yet know how, when, why, or how far an oil will 

 migrate. Gravitation, capillarity, different specific gravity of water 

 and oil (and some authors concede gas pressure) are the sum-total 

 of the admitted agents on migration, yet it is doubtful whether 

 any one of these has any primary effect on the initial movements of 

 the oil, and it is just these which are so important. Gravitation in 

 the accepted sense of the migration theorist requires free pore-space 

 for downward motion, but water-borne sediments will certainly be 

 water-clogged in their finer deposits. Capillarity will cause oil to 

 migrate in fine dry deposits, but it is a movement from the larger 

 pore-space to the smaller, not from the fine deposit to the coarse, and 

 in addition there is the same difficulty that the sediments will 

 almost certainly not be dry. The differential specific gravity of 

 water and oil will have its expected result in the proper conditions, 

 i.e. where the pore-space is large enough to allow a certain limited 

 circulation of liquids, but the hydrocarbons originate in the fine- 

 grained deposits, and it is just this initial migration from the fine 

 deposits to the contiguous coarse deposits wherein lies the difficulties 

 with the present theoretical ideas. When, however, the secondary 

 processes which take place in argillaceous sediments immediately 

 after deposition are examined, and the gradual diminution of pore- 

 space during compacting, with its necessary out-pressing of water and 

 other liquids, is taken into account, it is evident that here is a very 

 potent factor in the expulsion of liquids from fine material which 

 is easily compacted to coarse material which is more resistant to 



