502 
POPULAR SCIENCE REVIEW. 
Mr. Taylor has given the following explanation of this apparent anomaly : — “In 
various parts of Norfolk, as at Coltishall, &c., there lies at some height above 
the true Norwich crag, another bed of shells, varying in height from three feet 
to fifteen. These two beds are widely different in their organic remains, the 
upper bed being peculiar from the total absence of fresh and brackish water 
shells, those it has being marine ; secondly, the shells of the upper bed indi- 
cate that it had been formed in deeper water ; and thirdly, the shells are also 
of a more Arctic character.” The Norwich crag is everywhere distinguished 
by its littoral character, as also by the frequent occurrence of fresh and 
brackish water shells, constituting it a fluvio-marine deposit. Hitherto it 
has been the custom for geologists to class both these beds as belonging to 
the Norwich crag series ; hence the apparent difference between the latter 
and the crag. If the Norwich crag were confined solely to the beds always 
found resting on the chalk, it would approximate more nearly to the red 
crag ; but by taking the mean of the upper and lower beds, and summing 
up the total as belonging to the Norwich crag, they departed from the true 
character of each, as well as from their relations to the red and coralline 
crags. In his further observations, Mr. Taylor combats Mr. Searles Wood’s 
idea that the true Norwich crag is the representative of the red, by showing 
the difference in the shell deposits of the two. Mr. Taylor concludes, as we 
have already stated, that there are four crags. Vide paper read before the 
British Association at the Nottingham meeting. 
MECHANICAL SCIENCE. 
The most interesting contributions to scientific engineering duriug the past 
quarter are to be found in the papers read before the Mechanical Section of 
the British Association at Nottingham. Of these we may briefly enumerate 
the following : — 
Resistance of Water to Floating and Immersed Bodies . — Professor Kankine 
read the Report of the Committee appointed to make experiments on this 
subject, giving the results of 220 experiments, with two models, four feet in 
length. The Committee have deferred for the present deducing any general 
laws of resistance ; but Professor Rankine stated that the results of the ex- 
periments led to the following general conclusions. 1st. That agreeably to 
what was previously known of the behaviour of small bodies at low speeds, 
the resistance increased on the whole somewhat more slowly than as the 
square of the velocity. 2nd. That when the velocity went beyond the maxi- 
mum velocity suited to the length of the model, as ascertained by Mr. Scott 
Russell’s well-known rules, the resistance showed a tendency to increase at a 
more rapid rate. 3rd. In all cases the resistance seemed to be much more 
nearly proportionate to the mean girth than to the midship section. 4th. The 
resistance of model A when totally immersed to its own depth was almost 
exactly double of its resistance at the same speed when half immersed. 
5th. The resistance of model B when immersed to about three and a half 
