90 
THIRTEENTH REPORT. 
Transitional overlying the dolomite, during which time the present 
Silurian syncline was at least 700 feet wider than it is now, on the 
east side — for within that approximate distance the Transitional (of 
which there is 8 feet in depth at No. 10 hole,) has shored up; 
(6) Maximum thrust of uplift in close neighborhood of No. 10; 
(7) Change in elevations across the whole cross section distance of 
the Anderdon beds, with possible exception of the extreme western shore; 
and 
(8) Suggests the reason for the prevailing increased depths of 
boulder till from the eastern limit of the Malden Valley of Anderdon 
limestone, westward to Detroit river. — an ascertained increase of depth 
of from 12' 0" to 15' 0" to 21/ 3" to 28' 6" to 40' 0" at intervals of about 
700 feet. 
TRANSITIONAL ROCK. 
The characteristics of the Transitional rock at the base of the Ander- 
don limestone, and the reasons for describing it as transitional are these: 
il) It lies between a limestone deposit of the purest quality and 
an equally pronounced Silurian dolomite, and is itself a dolomitic lime- 
stone. 
(2) It is not local but extends over the whole area of, and beyond 
the outer edges of, the overlying Anderdon limestone; requiring, there- 
fore, consideration as a distinct deposit; and having characteristics 
that relate it to both the Devonian and the Silurian. 
(3) Like the Anderdon limestone above it, this rock carries the 
Devonian form of calcium carbonate crystal, dog-tooth spar, by contrast 
with the Silurian scalenoliedra of calcite. 
(4) Yet, in several instances, and at low horizons in the formation 
the crystals filling the cavities of the rock appeared to be a compromise 
between the two forms. 
(5) In addition to that fact, the prevailing browns, blue-grays, and 
the dullness of the grays and drabs are Silurian characteristics. 
(6) There were no Silurian forms distinguishable, nor either sul- 
phate or carbonate of strontia, nor any gashed or acicular rock; all of 
which, with scalenoliedra of calcite and high magnesia characterize the 
underlying strata. 
(7) There is, as in the Silurian, at many elevations, considerable 
dark-lined lamination and frequent irregular lines of deposit. 
(8) In three instances only does the CaCCK average of the transi- 
tional rock from a given test hole fall below 60%, and that where too 
few samples were taken. From all the rest of twenty-one averages the 
percentage of calcium carbonate is from 60.56 to 69.04. The average 
over all — in a distance of two miles — is 63.49 CaC0 3 . This fact estab- 
lishes the Transitional as a better calcium carbonate rock than is the 
heavy-bedded dolomitic limestone which lies second above it and forms 
the base of the Corniferous. This latter dolomitic limestone analyses 
about 60% CaCO... Like it, the Transitional appears to be almost fossil 
free. 
I submit that this rock is transitional in character, with predomina- 
ting Devonic features. 
Before considering the question of transitional rock at further length 
let me present some facts of 
