May 13, 1915| 
NATURE 
S1o5) 

‘compensated for temperature,” were in use when Mr. 
Fischer was first engaged on the Coast and Geodetic 
Survey. These gave place to 5-metre contact rods, 
consisting of a single bar of steel enclosed in a closely 
fitting wooden case, and covered with padded canvas. 
For use in the field they were mounted on _ tripods 
and placed end to end. In the hands of skilled ob- 
servers it was possible with this type of bar to attain 
a degree of accuracy approaching 1 part in 2,000,000. 
In the elaborate apparatus devised by Dr. R. S. 
Woodward a line bar was supported when in use on a 
steel trough and covered with crushed ice, the trough 
being carried by two trucks travelling on a portable 
track. Micrometer-microscopes were mounted on sup- 
ports fixed in the ground at carefully measured in- 
tervals approximately equal to the length of the bar. 
The operation of measuring was effected by bringing 
the bar under the first two microscopes and then 
setting the cross-wires of the micrometers on the lines 
of the bar; then without disturbing the reading of the 
forward micrometer the bar was displaced longitudin- 
ally until the line at its rear end was brought under 
the forward microscope, while at the same time an 
observer at the forward end set the micrometer on the 
line at that end, this process being repeated through- 
out the length of the base line. A kilometre base 
measured in this manner was estimated to have an 
accuracy of r part in 3,000,000. 
Eimbeck’s duplex base bars were next employed on 
the survey. These consisted of two concentric brass 
tubes in the inner of which a brass and a steel 
measuring bar were mounted. The inner tube could 
be rotated through 180° so as to equalise the tem- 
perature of the brass and steel components if one side 
of the apparatus should be more exposed to direct 
radiation. This method was in its turn superseded by 
the introduction of invar tapes. All primary bases of 
the United States Survey are now measured with invar 
tapes, tested preliminarily at the Bureau of Standards, 
and by this means base operations, while maintaining 
the high degree of precision which the work demands, 
admit of vastly greater rapidity in the field, with a 
consequent reduction in the expense involved. 
PLIOCENE MAN. 
HE discussion originated by the Rev. Osmund 
Fisher in Nature otf September 4, 1913 (vol. 
xcii., p. 6), has led to the systematic exploration, by 
a committee of the Dorset Field Club, of the Dewlish 
“elephant-trench,”’ and the report on the excavations 
was read at the anniversary meeting on May 4. 
This curious trench in the chalk yields bones of the 
Pliocene Elephas meridionalis, and Mr. Fisher sug- 
gested that it was artificial and dug for trapping the 
elephants. There can no longer be any doubt that 
the french was of natural origin. The elaborate 
plans, elevations, and photographs exhibited by Mr. 
Charles Prideaux, who superintended the excavations, 
show clearly that a few feet below the surface the 
supposed trench divides into a chain of pipes or pot- 
holes in the challx connected by a narrow joint. These 
become very narrow below; but one of them was 
traced to a depth of 36 ft. One or two of the smaller 
pipes still show traces of the lining of black clay 
commonly found in pipes caused by solution in the 
chalk; the larger ones were filled with chalky sand 
full of flints, and Tertiary material; many of the 
flints were beautifully polished. Flakes caused by 
sudden changes of temperature were also abundant. 
Mr. Clement Reid discussed the geological evidence. 
He thought that it proved the existence of a fissure or 
joint transverse to the valley of the Devil’s Brook. 
Along this joint a chain of pipes was formed by the 
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action of percolating rain-water. Then the pipes 
nearest to the valley-bottom acted as ‘‘ swallow-holes,’’ 
into which the brook sank, the constant swirl of the 
water laden with calcareous sand giving the flints 
the wonderful polish now seen. In short, the Devil’s: 
Brook, then flowing at a level oo ft. higher, was a 
“winter bourne,” which at Dewlish, for part of the 
year, at any rate, was swallowed up and disappeared. 
into these pot-holes.. Such pot-holes are common in 
the Carboniferous Limestone, though rare in the 
Chalk. This chain of pot-holes acted as a natural 
pitfall, into which the elephants fell, or into which 
their bones were washed; thus far Osmund Fisher 
was right in calling it an ‘“‘elephant-trap,” though it 
probably had a natural origin. Mr. Reid saw  no- 
sign of human agency in the trench. The date ot 
the deposit must still remain somewhat uncertain, 
for all the determinable bones belong to EL. meri- 
dionalis, and this species, though mainly Pliocene, 
may have lived on into early Pleistocene times. 
Mr. Reid Moir, in another report, described a num- 
ber of the flints as showing undoubted human work- 
manship of eolithic type. Mr. Reginald Smith, how- 
ever, after an examination of the same specimens, 
thinks that one or two of them may possibly be 
worked, the others he rejects. 
A report by Mr. Dewey pointed out that a sample 
of calcareous sand from the trench proved under the 
microscope to consist mainly of minute rhombs of 
calcite, such as would be precipitated from a saturated 
solution. This he thought pointed to an arid climate- 
SYSTEMATIC ZOOLOGY OF THE 
INVERTEBRATA. 
PACTONG recent systematic papers on the inverte- 
brates, a noteworthy account of the parasitic 
worms collected on the British Antarctic (Terra Nova) 
Expedition, written by Dr. R. T. Leiper and Dr. 
E. L. Atkinson, has been published by the British: 
Museum (‘‘Terra Nova Zoologv.’’ vol. ii., No. 3)- 
From the summary of results we learn that the Ross 
Expedition of 1841-4 brought back two species of 
Entozoa; the Scott (Discovery) Expedition of 1901-4 
four species; the Bruce (Scotia) Expedition seventeen 
species; the French (Pourquoi Pas?) Expeditiow 
eighteen species; the Terra Nova twenty-eight species. 
These figures show how greatly zoological knowledge 
has been increased through our latest national Ant- 
arctic enterprise. Three of the worms now recorded 
from the far south had previously been known only 
from the Arctic regions. Two of these—a Filaria and 
an Echinorrhynchus—have whales as their hosts in 
both localities, but the third—a monostomid trematode, 
Ogmogaster plicatum, Creplin—is parasitic in rorquals 
in the north, and in the Crab-eating and Weddell’s 
Seals in the south; a remarkable divergence in habit. 
From home waters there is still much material to- 
be gathered, and C. M. Selbie’s important paper on 
the Decapoda Reptantia of the coasts of Ireland, part 1 
(Fisheries, Ireland, Sci. Invest., 1914, i.), adds to the 
fauna of the Britannic marine area the family 
Eryonide, as represented by four species of Polycheles 
and four of Eryonicus. These were all taken in deep 
water off the west coast of Ireland, though the speci-- 
mens of Eryonicus ‘‘lead a free-swimming life at a 
considerable distance from the bottom.’’ The paper 
is illustrated by fifteen excellently drawn plates. 
A very important paper on those interesting copepod” 
fish-parasites, the Lernzopodida, has been published 
by C. B. Wilson in the Proc. U.S. Nat. Museum (vol. 
xIvii., pp. 565-729). Though dealing especially with 
species from North American waters, the author gives 
a revision of the whole family, thus affording a trust— 



