Reviews and Book Notices. 
249 
necessity for disposing of the waste liquors from the factories 
which increase in size and numbers, all mitigate against a 
return to the “ good old times.” But the Ministry of 
Agriculture and Fisheries considers that the work done in 
East Yorkshire by amateur zoologists, botanists, and chemists, 
might easily be undertaken in other areas.’ The British 
Association paid Mr. Sheppard the compliment of announcing 
that they had decided to print his report in full. 
FIELD NOTES. 
Theba cartusiana Mull., etc. — I have recently obtained 
specimens of Theba cartusiana Mull, and Helicella itala L. 
at Charlottenlund Fort near Copenhagen. In The Naturalist , 
1916, page 61, I gave a notice of the occurrence of Theba 
cartusiana Mull, and Helicella ‘ candicans Zgl.’ at * the 
fortress near Jgegersborg near Copenhagen ’ (= Charlottenlund 
Fort). Unfortunately it was during the war, and I was not 
allowed, personally, to visit the place. My records were 
doubted (see Taylor’s Monograph, Part 23, 1917, page in 
(under Theba cartusiana). As Charlottenlund Fort was 
recently opened for the public, I examined the ramparts 
there, and found both species in great numbers, and also a 
sinistral specimen of Helicella itala L. Most of the Helicella 
itala, however, are very planulated, therefore I have named 
it ‘ candicans ’ =obvia Hartm. 17 years ago. — Hans Schlesch, 
Copenhagen, Denmark. 
Ringed Carrion Crow. — On July 24th Mr. Usher, head 
gamekeeper to Capt. B. H. Croft, of Malham Tarn, shot a 
young Carrion Crow on Fountains Fell, with a ring on its leg, 
and he was very much puzzled to know how the ring got there, 
so he sent the ring on to me. It was one of Witherby’s and 
was numbered RT6701, and Mr. H. F. Witherby has kindly 
informed me that it was ringed as a nestling at Giggleswick 
on May 14th, 1933, so that it had not got very far on its 
travels.- — H. B. Booth. 
Mimicry, by G. D. Hale Carpenter and E. B. Ford. Published 
in Methuen’s Monographs on Biological Subjects, ix+134 PP-» 3 /6. 
This is a valuable addition to the library of the entomological student. 
The authors are themselves convinced of the reality of mimicry, and 
in the short space at their disposal make out a fairly reasoned case. 
The references are numerous and are gathered from a very wide field. 
Collision Processes in Gases, by F. L. Arnot. Published in 
Methuen’s Monographs on Physical .Subjects, viii+104 pp., with 37 
diagrams, 3/-. This is a short account of recent work on ‘ collision 
processes in gases at pressures such that the mean free paths of the colliding 
bodies are so large relative to the dimensions of the apparatus that the 
effects can be studied.’ It should prove useful to the advanced student 
of this branch of physics, saving him an immense amount of labour in 
looking up the literature. 
I 933 Nov. 1 
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