40 
PRINCIPLES OF BIOLOGY. 
reached by mines or deep bore holes ; and lastly, the probable 
manner in which they extend underground between the 
points where their presence has been actually determined. 
Only those points will be considered in detail which have 
not been already published. 
Surface Exposures of Pre-Carboniferous Iiocks. —The ancient 
rocks which we have to describe crop out as “ islands ” 
or “bosses,” along a line from south-west to north-east, 
extending from the Malvern Hills, by the Wrekin, the Lickey 
Hills, and the Hartsliill Range to Charnwood Forest in 
Leicestershire. 
1 .—The Archaean Rocks of Charnwood* —Charnwood 
Forest is a hilly rocky tract of about thirty square miles, 
lying between the towns of Leicester, Loughborough, and 
Burton. The rocks consist of coarse slates, grits, and 
agglomerates, about ten thousand feet in thickness, and of 
volcanic origin. They strike from north-west to south-east, 
and are broken through by syenitic and granitic masses, with 
the result that at one point (Brazil Wood) the slate has been 
converted into a micaceous schist. The Charnwood axis is 
continued to the south-east, beneath the Triassic strata of 
South Leicestershire, being overlaid in that direction by 
Cambrian rocks presently to be described. The ashy slates 
of Charnwood are believed to be of Archaean or Pre-Cam¬ 
brian age, for the following reasons :— (a) they agree well, 
both when studied in the field and when examined micro¬ 
scopically, with the Pebidian Formation of Dr. Hicks ; (b) they 
have yielded no fossils of any kind ; (c) they are certainly 
overlaid by Cambrian strata, although the junction is con¬ 
cealed from view by newer beds. 
(To be continued.) 
THE PRINCIPLES OF BIOLOGY. 
BY HERBERT SPENCER. 
EXPOSITION OF CHAPTER VII.-GENESIS. 
BY W. B. GROVE, B.A. 
Genesis is the multiplication of individuals. In the cases 
most familiar to us this takes place in such a way that like 
produces like, the offspring closely resembles the parent. 
But modern science shows us that this is not the most 
* See “ Geology of Leicestershire,” by W. J. Harrison; and Hill 
and Bonney, Quart. Jour. Geol. Soc. 
