504 W. Whitaker — On Geology and Consumption. 



basin of sand or gravel on clay is favourable for tbe holding rather 

 than for the flowing off of water. From this comiiarison, it was 

 found that districts mainly on a set of pervious beds (whether of 

 gravel over London Clay, of the sandy and pebbly Lower London 

 Tertiaries, of Chalk, or of Lower Greensand) and which have a fair 

 general height, and a fair slope of surface, have a lower consumption 

 death-rate than other districts on the same formations, but at lower 

 levels, and with flatter surfaces. 



There is one remarkable kind of exception to this rule. It is that 

 the low-lying tracts of shingle bordering the shore, and saturated 

 more or less by sea-water, seem to be not badly off in respect of 

 consumption, — Dover, where a large part of the population live on 

 shingle, being a notable case in point. 



Thirdly, districts chiefly of impervious formations were examined 

 with regard to their physical features ; the higher and more sloping, 

 which allow of the flowing off of surface-water, being compared 

 with those that are lower and flatter, and on which therefore water 

 rests longer. This of course was little more than a comparison of 

 the two great clay-tracts, those of the London Clay and of the Weald 

 Clay, the physical differences of which have been noticed before 

 (p. 502). 



The gravel-covered London Clay ranges itself amongst the per- 

 vious formations, but a comparison of the two clays when bare 

 shows a great difference in their consumption death-rate. Many 

 districts have a goodly jDropoi'tion of their population on the sloping 

 London Clay without their consumption being much affected, 

 whereas in those that have much population on the flat Weald Clay 

 the death-rate is high ; so that here again wetness and consumption 

 go together. 



The few exceptions are perhaps one of the best proofs of the 

 rule. On those parts of the South Coast where a large population 

 lives on London Clay the consumption is very high, — Chichester 

 indeed standing worst of the fifty-eight districts. Now in that 

 country the London Clay has not its usual features, but forms a 

 more or less gravel-covered, low-lying, water-logged flat, being 

 (exceptionally) much in the usual condition of the Weald Clay. 



As the shingle-tracts bordering the sea seem to be an exception to 

 the rule that low-lying pervious beds are much worse off than those 

 at higher levels ; so the alluvial flats bordering the sea seem to form 

 an exception to the rule amongst impervious beds, the striking case 

 being Sheppey, which stands at the head of the whole fifty-eight 

 districts, although the greater part of its population live on alluvium, 

 close to tlie sea, and at about the sea-level. One is led to think 

 therefore that saturation by sea-water and saturation by fresh- 

 water are quite different matters, and that whereas the latter 

 increases the consumption death-rate, the former is comparatively 

 harmless, or perhaps even beneficial. Sea air too may be good for 

 consumptive patients. 



The conclusions that result from the geological and statistical 



