APRIL 29, 1915] 
NATURE 
243 

with those of younger colleagues. One of the most 
striking features of the district is the Great Glen 
fault, which, despite its Caledonian trend, is later 
than some of the folding of the Old Red Sandstone, 
and has here a minimum throw of 6000 ft. 
The river-scenery is finely illustrated, and attention is 
directed (p. 82) to a deep pre-Glacial channel at the 
mouth of the valley of the Ness, the rock-floor of 
which has not been reached at 290 ft. below Ordnance 
datum. The Strathpeffer Spa, with its  sulphur- 
bearing springs, is the main economic feature of the 
district. In a region so rich in human history, we 
wish that a geological survey might trench farther on 
the field of the geographer and the archeologist. 
Drs. Peach and Horne have provided a description 
of the ‘‘Geological Model of the Assynt Mountains”’ 
very large area. We miss a reference in the memoir 
to the old tale of the ‘t Caithness grin,’? which. was 
said to be developed among a hospitable folk by sight- 
ing a stranger across miles of level flagstone. The 
evidence for a Middle Old Red Sandstone Series, 
which was sustained by J. W. Evans in 1891, is fully 
substantiated in this memoir, in consequence .of the 
studies made by Traquair on the fossil fishes. These 
include the interesting Palaospondylus at Achanarras. 
We should like to have a further account of the flora 
of the Caithness strata, beyond the brief references on 
pp- 5 and 81. The successive stages of deposition of 
the Old Red Sandstone in ‘* Lake Orcadie”’ are well 
shown in diagrams on pp. 84 and 85. A downward 
warping of the Caledonian continental surface allowed 
of the accumulation, as Sir A. Geilie long ago esti- 

Thurso Flags (Upper Caithness Flags) cut bya typical ravine or ‘‘ goe,” south of Duncansby Head. 
Reproduced from the Memoir to Sheets rro and 116, by permission of the Controller of H.M. Stationery Office. 
(1914, price 1d.), which is exhibited in the Museum 
of Practical Geology, the Royal Scottish Museum, 
Edinburgh, and elsewhere. This modestly priced 
pamphlet, with its numerous sections, forms an excel- 
lent introduction for the student to the classic district 
of the Highland overthrusts. 
The memoir to Sheets 110 and 116, entitled ‘t The 
Geology of Caithness’’ (1914, price 4s.), is by C. B. 
Crampton and R. G. Carruthers. The maps (2s. 6d. 
each) with the memoir show a thinly populated country 
formed mainly by Old Red Sandstone, and descend- 
ing from the Highland region northward, until it 
becomes, in comparison, a plain with ‘‘monadnocks,”’ 
now stretching at about 150 ft. above the sea. Peat, 
as the useful system of shading shows us, covers a 
NO. 2374, VOL. 95 | 


Many of these ‘‘ goes" are of pre-Glacial origin. 
mated, of some 16,000 ft. of Caithness flags. The 
origin of red strata in a warm and fairly dry climate, 
where vegetation exists, but not in sufficient quantity 
to acidify the soil, is discussed in chapter ix. The 
considerable amount of calcium carbonate in the flag- 
stones is attributed to an arid epoch, here called a 
cycle, affecting the deposits on the shores. 
The suggestion (p. 100) of the sudden suffocation 
of fish by the inflow of alluvium is supported by a 
recent observation of E. Kolb during his descent of 
the Arizona canyons. The gills of the fish were, how- 
ever, in this recent case choked by mud during flood- 
ing of the stream, and not in a period of marginal 
recession. 
The nearness of Cretaceous 
masses to the north- 
