128 ME. C. E. TILLEX OX THE GrRAyiTE-Cr^-EISSES [vol. Ixxvii, 



(1) St. Lawrence County (Xew York). — C. H. Smvth,^ in a 

 short report on the crvstalline rocks of this county, describes a 

 series of gneisses associated with metamoii)hic hmestones. The 

 special point on which remark is necessary, is the rehitionship of 

 certain basic bands in the igneous gneisses. These present features 

 which are closely similar to those of the Flinders Series. In 

 referring to the relations of the gneisses to the intercalated bands, 

 Smyth remarks (p. 491) : 



' The possibility of the black bands being segregations in an igneous rock, is- 

 for the typical cases excluded by their form, although it may be applicable to 

 some occurrences. There remains the supposition that the black bands are 



fragments of an older gneiss included in a gneiss of igneous origin the 



bands owe their shape to their breaking from the parent mass, as they would 



in the direction of least resistance The i^arallel arrangement of the 



neighbouring bands doubtless results from currents in the molten magma, 

 which woTild tend to produce such a result. It is probable that the breaking 

 into blocks resulted in part from stresses applied after the magma was in a 

 pasty and partially crystallized state. The blocks were more or less widely 

 separated and the intervening space was filled by the magma which flowed 

 around the blocks without destroying their angular contour, and at the same 

 time often produced an obsciu-e flow-sti'uctnxe in the gneiss parallel to the 

 sides of the inclusions. 



' The fijie fissures and cracks were filled with the more acid portions of the 

 magma, which were last to crystallize, and were strained into these cracks 

 producing the coarser pegmatitic veins.' 



A consideration of the foregoing passages and of other facts 

 Avhich are adduced in the original paper, suggests that there is a 

 remarkable resemblance between the relations of the basic bands 

 and the enveloping gneisses for the two areas. 



It is, however, not only in the Xew York region that parallels 

 can be discovered for the features expressed in the Flinders 

 gneisses. The work of Prof. F. D. Adams & Xr. A. E. Barlow in 

 the Haliburton-Bancroft area of Ontario,- has shown that there 

 is in this Laurentian ti-act a widespread development of basic 

 amphibolitic bands within the granite-gneisses, exhibiting relations 

 identical Avith those seen in the amphibolites of the Eyrian region. 



(2) The Haliburton-Baneroft area (Ontario). — It is perhaps 

 this region that bears the closest analogy in the structural com- 

 position and jDctrographical character of its Pre- Cambrian rocks 

 to the Eyrian Pre-Cambrian. The oldest rocks of the area, the 

 Grrenville Series, afford a comparison with the Hutchison Series. 

 Carbonate sediments now highly metamorphosed and paragarnet- 

 gneisses of quartzitic and shaly composition are common to both 

 series. In the siicceedino; Laurentian Svstem, the gneisses with 

 primaj-y tlow-structure, and theu- included amphibolite-bands, hnd 

 parallels in the Flinders Series of gneisses. 



Adams & Barlow have recognized amphibolites arising in more 



1 New York State Mus. Eeport 49 (1895) pp. 4S1-97. 

 - Mem. Geol. Surv. Canada. Xo. 6. 1910. 



