200 Intelligence and Miscellaneous Articles. 



it is converted into a foliated arnphibolite. Apart from these rocks 

 there are developed, cutting the gneisses, posterior d} r kes of basic 

 charnockitic type (noritic). 



Xenoliths of sedimentary origin, and derived from the pre- 

 existing Hutchison Series, occur in the Sleaford area. They com- 

 prise diopside-rocks (para-pyroxenites), garnet- biotite-schists, and 

 peculiar garnet-spinel-sillimanite nodules. 



The amphibolites are considered as representing more basic and 

 earlier igneous intrusions — probably of the same igneous cycle, and 

 connected with the one great orogenic epoch — which have become 

 thermally metamorphosed, both prior to, and consequent on, 

 engulfment and incorporation in the granite-gneisses. 



Intercalated in bands in the gneisses of certain portions of the 

 hundred of Lincoln, is a series of dolerites which have suffered 

 a metamorphism of the highest grade. The pyroxenes and fel- 

 spars have been recrystallized, the former in granulitic aggregates. 

 Garnet has been abundantly produced. By a degradation of a 

 complex pyroxene-molecule, garnet, hypersthene, and a diopsidic 

 pyroxene have arisen. The metamorphism expressed in these 

 dolerites is of the high-grade thermal type, and it is thought 

 probable that the changes induced have resulted from the incor- 

 poration of earlier dolerites within the granite magma. The field 

 evidence so far gathered does not, however, permit this view to 

 be regarded as proven. 



In structural composition and petrographic character, the Eyre 

 region bears a striking resemblance to the Laurentian tract of 

 North America, and particularly to the Haliburton -Bancroft area 

 of Ontario. 



XXIV. Intelligence and Miscellaneous Articles. 



SOME PROBLEMS RELATING TO ROTATING FLUID IN THE 

 ATMOSPHERE. 

 To the Editors of the Philosophical Magazine. 

 Gentlemen, — 



IN the paper under the above title published in the April number 

 of the Philosophical Magazine, a second-order term has been 

 omitted from equations (A) given on page 66f>. The term 

 + w x lu)i / y + h) z (z + Tl)~] should appear on the left-hand side of the 

 adequation of motion, and corresponding terms in the y and z 

 equations. 



These additional terms do not appear at all in Case I. of the 

 fluid motions considered in the above paper, and they are negligible 

 in Cases II. and III. Owing to these terms, however, the conti- 

 nuity equation (19) in Case IV. is not satisfied, and Case IV. ac- 

 cordingly does not give a solution accurate to second-order terms. 



In the third equation of equations (A) and (18) respectively 

 (w z 2 + w/) should be multiplied by (z + 'R). 



It should be noted also that a constant due Eastward velocity 

 U of the rotating fluid is represented by an increase in the value 

 of 12, and this accordingly affects the value to be used for io 2 as 

 well as that for wy in the motions considered in Cases II. and III. 

 University of Glasgow, • George Green. 



April 28, 1921. 



