8 NATURE 
’ 
Character of Metalliferous Deposits” was of 
special interest to economic geologists and mining 
engineers. Kemp dealt generally with primary 
and secondary precipitation; Krusch with colloidal 
precipitation of primary and secondary ores; 
Emmons with experimental evidence bearing on 
the precipitation of gold, silver, and copper, and 
the effect of the primary ores; Fermor with the 
action of oxygen and carbonic acid at considerable 
depths; Fanning with ore occurrences in the Phil- 
lipines. In the general discussion, in which 
Lindgren, Winchell, Lawson, Kitson, and others 
took part, the question of the formation of veins 
consequent on mineral crystallisation, and that of 
secondary gold deposition from placers, were 
taken up. 
What were perhaps the most interesting dis- 
cussions to the majority of the members of the 
congress were those on the sedimentation and the 
correlation of the Precambrian. The excursions 
provided to the vast Precambrian areas of Ganada 
had attracted to the congress authorities from the 
Precambrian fields in all other countries; and the 
discussions were illuminating in that they focussed 
the experience of work in many fields on the intri- 
cate problems presented. The succession in Fin- 
land was given by Sederholm, who also illustrated 
by slides some clear instances of granitisation on 
a regional scale. Cole explained the intrusive 
relationships in north-west Ireland. The difficul- 
ties encountered by Scottish geologists in correlat- 
ing the Precambrian of the Highlands were ex- 
plained by Horne. An outline of the Precambrian 
of the British Isles was given by Strahan. Holland 
pointed out the broad similarities between the 
series in India and in North America. Coleman 
and Collins dealt more particularly with the area 
east of Lake Superior. A rather keen discussion 
took place when the classification submitted by 
Lawson as based on work in the Rainy Lake area 
was questioned by Leith and Lane. Altogether 
the session was illuminative of the difficulties in 
the way of any attempt to correlate the Precam- 
brian in widely separated areas. 
Other topics considered can only be mentioned 
in brief. On the physical and faunal character- 
istics of Paleozoic seas papers were presented by 
Chamberlin, Schuchert, Ulrich, Frech, and 
Holtedahl. To the topic of interglacial periods 
Lamplugh, Coleman, Upham, Alden, Tyrrell, 
Wolff, and Holst contributed; while at a special 
session on tectonics papers were given by 
Paulcke, Dahlbiom, Mess, and Smith, McDonald, 
Howe and Hovey. Numerous miscellaneous 
papers were also submitted dealing with subjects 
of geological and mineralogical interest. 
During the session of the congress two popular 
lectures were delivered, to which the Toronto 
public were invited. The first was by M. Em- 
manuel de Margerie on the geological map of the 
world. The lecturer gave some very practical 
1 The discussion had at least one permanent result. A resolution proposed 
by Dr. Sederholm was passed by the Congress to the effect that geological 
surveys of countries which have contiguous areas of Precambrian rocks form 
international committees to include representatives of the geological surveys 
of all the countries concerned, for the purpose of correlating the Precambrian 
formations in the different countries. 
NO. 2288, VOL. 92] 
[SEPTEMBER 4, 1913 
suggestions to the committee in charge of the 
preparation of the map. He advocated the con- 
tinental as opposed to the World map, and the 
discrimination by colour between marine and 
lacustrine sediments, and between folded and un- 
folded areas. The continental areas were dis- 
cussed seriatim, with practical hints as to map- 
construction. Of more interest to the general 
public was a lecture by Dr. W. F. Hume on desert 
phenomena in Egypt. The lecture, which was 
illustrated by slides, presented a clear picture of 
the geological conditions, and in particular of the 
effects of sand erosion on the exposed rocks. 
Much could be inferred from the slides as to the 
actual conditions under which work is carried on 
in desert countries. 
Notwithstanding the interest evinced in papers 
and discussions, the value of the twelfth congress 
to the visiting delegates lay mainly in the excur- 
sions which they were enabled to undertake to 
many points of geological and mining interest 
throughout the Dominion. Elaborate preparations 
had been made by the Geological Survey of 
Canada to ensure the success of this feature of the 
meeting, and the total length of line covered by 
the guide books considerably exceeded 20,000 
miles. From July 13 to September 23 excursions 
practically without a break were arranged for 
—frequently three, or even more, concurrently. 
The maritime provinces were visited, before the 
session, under the guidance of Dr. G. A. Young; 
Sudbury, Cobalt, and Porcupine before and after 
the session, the excursions being led by Dr. W. G. 
Miller; while two transcontinental excursions, the 
first of more particular interest to petrologists and 
stratigraphers, the second to economic geologists 
and mining engineers, had as leaders Dr. Adams 
and Mr. Brock respectively. An excursion of 
particular interest, of which many would have 
gladly availed themselves had time permitted, was 
that to the Yukon and Alaska boundary, led by 
Mr. McConnell. Besides these longer excursions 
numerous field-trips were made, both before and 
during the session in Toronto. To the localities 
in the vicinity of Toronto Dr. Coleman and Dr. 
Parks acted as guides. 
For the excursions a series of guide-books was 
prepared by the Geological Survey of Canada, 
which contained besides the reading matter numer- 
ous coloured maps, topographical maps, and 
photographs. Apart from the immediate value to 
the members of the congress, the guide-books 
represent an important contribution to Canadian 
geology. They summarise a large amount of 
investigation accessible only in the reports of the 
survey, and contribute as well a considerable 
proportion of new material. They cover the main 
routes of travel, and will prove valuable books of 
reference, not only to geologists and engineers, 
but also to any travellers who may be interested 
in the resources and rock formations of the 
country. The interest which the excursions had 
aroused in Canadian geology was shown by the 
eagerness with which the literature supplied by 
the Geological Survey and mines branches was 
sought after. From this point of view the con- 
