3574 
spark is formed across the gap and the charge is thus 
conducted to earth. As now the electromotive force 
required to maintain an arc is much less than that 
required to start it across a gap, the arc is maintained 
by the ordinary voltage of the system, and has to be put 
out by some other means. Upon the methods adopted 
to do this Dr. Benischke bases his classification of the 
various arrestors as follows :—(1) An arc is not allowed 
to form by reason of the dividing up and cooling of the 
spark ; (2) arc broken mechanically ; (3) arc broken by a 
magnetic blow out ; (4) arc broken by its own magnetic 
and thermal action ; and (5) arrangements containing a 
large resistance in the earth connection. 
This classification is all very well, but in our opinion 
does not give one a proper standpoint from which to 
iudge of the value of the protection afforded. 
Recent investigations have shown that the formation of 
an arc in the circuit of an underground cable is, in 
certain circumstances, attended with very grave danger. 
An arc in sucha circuit, between horns, as, ¢.g., in the 
Siemen’s or the Allgemeine Elektricitats Gesellschaft’s 
arrestors, whether it is blown out by a magnet or by its 
own action on itself or other means, is very liable to 
produce those very rises in potential which it is the 
-object of the arrestors to obviate. This very important 
consideration is not mentioned by the author. That, 
however, it is true is borne out by the fact that, in many 
English alternating-current high-tension stations, origin- 
ally fitted up with spark-gap arrestors, their-use has been 
attended with such bad results that they have been given 
up. Even if such so-called arrestors are scientifically good, 
it is very questionable if they can be made of practical ser- 
‘vice for high-tension systems by reason of their inherent 
want of sensitiveness. In support of this contention it may 
‘be mentioned that on p. 32 the author gives as an example 
of great sensitiveness the adjustment of the gap so that 
it will go acrossat double the working voltage. We are 
very certain, however, that there are very few high-tension 
underground cable systems which have such a large 
factor of safety. In, for example, a 5000- or 6000-volt 
system which has been running for some time, a rise of 
but 2000 or 3000 volts above the working pressure is 
generally sufficient to break the insulation down some- 
where. In purely overhead lines the case is somewhat 
different, as it is very much easier here to make the 
insulation with a much larger safety factor. 
In our opinion the proper arrestor for high-potential 
lines has yet to be designed. It must be so adaptable 
to the circuit on which it is placed that by its action no 
danger of rises of potential due to it can occur. By 
proper adjustment of its dimensions to the electrical 
constants of the circuit this can, perhaps, be arranged. 
The arrestors classified by the author under No. 5 are, 
in our opinion, the most hopeful. In places like South 
Africa, where static charges are of constant occurrence, 
this form is the only one that has given any good result, 
on, of course, low-tension circuits. ‘Their development 
for high tension is, however, a thing of the future, and 
has to cope with many difficulties, some of which are 
indicated in the book by the author. 
Dr. Benischke’s book is to be welcomed as a valuable 
contribution toa subject to which as yet so little attention 
thas been paid. €.'G.)G. 
NO. 1719, VOL. 66] 
NATURE 
[OcTOBER 9, 1902 
OUR BOOK SHELF. 
Catalogue of Scientific Papers (1800-1883), Supple- 
mentary Volume. Compiled by the Royal Society 
of London. Vol. xii. Pp. xxxii + 807. (London: 
C. J. Clay and Sons, 1g02.) 
THE readers of NATURE must be so familiar with the 
“ Royal Society Catalogue” that it is needless to give any 
description of it ; suffice it to say that when the work for 
the decade 1874-1883, printed in vols. ix. to xi., was in 
progress, it was found that a considerable number of 
periodicals had been omitted, many of which contained 
valuable papers. As stated in the preface to vol. ix. 
the President and Council contemplated the publication 
of a supplementary volume which should contain the 
most important papers that appeared between 1800 and 
1883 in periodicals not hitherto catalogued. 
A preliminary list of the omitted serials was made, 
and after a careful sifting it was found that 355 remained 
to be dealt with, the titles and abbreviations of which 
occupy twenty-six pages of the volume. These were 
catalogued in the same way as the previous portion of 
the work, but when the* matter was prepared for the 
press it was evident that the amount to be printed was 
much greater than had been anticipated ; the committee 
therefore decided that references to abstracts of papers 
that had appeared in previous volumes should be ex- 
cluded, that all references to abstracts should be excluded 
except in the cases of papers in some other language than 
English, French, German, Italian or Latin, abstracts of 
which had been published in one of these languages, and 
in such a case reference was to be made to only,one 
abstract. The effect of this curtailment was to reduce 
the work to about 800 pages. 
The papers of each author are numbered as in the 
previous volumes ; it must be noticed, however, that 
these numbers no longer represent the chronological 
order of publication. 
Great care has been taken to ensure accuracy in the 
references, and many corrections of errors discovered in 
previous volumes have been made. Much credit is due 
to Miss Chambers and Miss Bremner and the ladies 
working under them, and also to the late Mr. George 
Griffith, who acted as editor. 
The Early Life of the Young Cuckoo. By W. P. 
Westell. Pp. 26; illustrated. (London: Burleigh, 
1902.) Price Is. net. 
IN this little volume the author gives an account of the 
observations made by Mr. J. Craig, of Ayrshire, during 
the summer of 1899, as to the manner in which young 
cuckoos eject the other occupants of the nest in which 
they happen to have been hatched. Two of the photo- 
graphs illustrating the work have appeared previously in 
the Amateur Photographer of November 28, 1901, in 
connection with a lecture by Mr. J. P. Millar ; and it 
would perhaps have been better if the author had 
definitely informed his readers of this fact instead of 
merely stating that Mr. Craig’s “photographs and ob- 
servations have by this time been heard of throughcut 
the ornithological world.” 
Smce Mr. Craig’s observations have not been pre- 
viously referred to in NATURE, they may be briefly 
noticed on the present occasion. At the commence- 
ment of June, 1899, Mr. Craig found a titlark’s or 
meadow-pipit’s nest containing five eggs, two of which 
were those of cuckoos. One of the titlark’s eggs was 
broken in order to ascertain how long it had been 
brooded. In due course two young cuckoos were 
hatched out, one of the titlark’s eggs being by this 
time broken and the other missing. One cuckoo soon 
succeeded in ejecting its fellow by carrying it on its 
back to the edge of the nest and tilting it over in the 
manner shown in the illustrations. The same process 
