at intervals by Herr Oldenbourg, of Munich. 
>. = 
NATURE 
" walls of class-rooms. They are certainly to be compared 
with maps for the range and precision and correlation of 
parts with which they show their contents at a glance. 
‘Mg E. B, TYLOR 
ug 
OUR BOOK SHELF 
Aus der Urzeit. Bilder aus der Schépfungsgeschichte, 
von Prof. Dr. Karl A. Zittel, in Miinchen, Mit 78 Halz- 
schnitten. (Miinchen: Rudolph Oldenbourg, 1871-2.) 
THIS is one of a serics of popular works on Science 
entitled “Die Naturkrifte,’ that are being published 
Prof. 
| Zittel, in his preface to the present work, speaks of 
_ that is characteristic or informing. 
the vast influence which popular scientific litera- 
ture is calculated to have upon the entire development 
of a people, and therefore insists on the great im- 
portance of diffusing, in an intelligible manner, among 
the people thoroughly correct notions of every science, in- 
stead of mincing down scientific truths until they lose all 
It is, perhaps, of far 
more importance that scientific books meant for the 
people should be as absolutely correct and as far ad- 
vanced as it is possible to be, than those intended for 
_ scientific men themselves. 
_ reject the false or imperfect ; the former in their ignor- 
ance accept what is written as the truth, and the injury 
_ thus done is often serious in its consequences and may 
The latter can discover and 
take a generation or longer toremedy. Popular scientific 
works, like school text-books of science, ought to be 
written only by those who are thoroughly masters of their 
subjects. 
respect satisfactory. In a series of chapters, each 
_ corresponding mainly with one of the great geological 
periods, the author endeavours to present a series of 
pictures of the gradual development of our earth, mainly 
with reference to the life which it supports. He seems to 
know his subject well in all its aspects, and present$ in an 
_ interesting and intelligible way the latest results of geolo- 
gical research, with the conclusions derived therefrom by 
the most advanced thinkers. The illustrations are very 
good, and the work as a whole is a good specimen of a 
popular scientific treatise. 
LETTERS TO THE EDITOR 
r [ The Editor does not hold himself responsible for opinions expressed 
by his correspondents, 
No notice ts taken of anonymcus 
communications. | 
Remarkable Phenomena 
Ty may be within the memory of some of your readers that 
between the 15th and 2oth August, 1868, a succession of waves 
reached Sydney, and were recorded by the self-registering tide- 
gauge. The average interval between the waves was about 25 
minutes, and the greatest oscillation 34 inches, measuring from 
the crest uf one wave to the hollow of the next. It was thought 
at the time that they were earthquake phenomena. 
A similar visitation has just reached us, but it was not so 
marked in its character. The self-registering tide-gauge shows 
that the disturbance began during the afternoon of the 15th, and 
attained its maximum between 1 A.M. and 4 A.M. of the 17th, 
the greatest oscillation, amounting to 5 inche-, occurred between 
3.15 A.M. and 3 33 A M. o! the 17:h, the average interval of the 
waves at this time was 25 minutes, but the average of 20 between 
8 P.M. and 5.30 A.M. was 28 minutes. The waves cannot be 
traced beyond the 18th, 
On the afternoon of the 16th we had a thunderstorm, during 
which the barometer was very unsteady, and the barograph 
sheets show some peculiar curves ; strange to say, the average 
The book before us seems to us to be in this. 
547 
interval of the 5 most conspicuous of the barometer curves or 
waves between 5.40 P.M. and 7.30 P.M. is 25 minutes ; the largest 
oscillation was 0'045 in. of mercury, equal to about 6 inches of 
water. Just before daylight on the morning of the r7th several 
fine meteors were seen to N.E., but the observer who reported 
them to me did not make notes of particulars. At Newcastle, 
which is a port 60 miles north of Sydney, I have another selt- 
registering tide-gauge, which recorded a disturbance similar to 
the Sydney one ; it began on the afternoon of the 15th and was 
greatest between 8 P.M. of 16th and 7 A.M. of 17th ; the greatest 
oscillation, 9 inches, occurred between 12.15 A.M. and 
12.30 A.M. of 17th, and the average interval of all the waves 
from 8 P.M. to 5.3 A.M. of 17th, amongst which are several that 
only occupied 5 minutes, and look like double oscillations, is 20 
minutes, 
Struck by the circumstances that both sets ot waves, though 
separated by an interval of 5 years, occurred in August, I deter- 
mined to examine all the tide-gauge sheets since 1866, when the 
instrument was set up, and was surprised to find a repetition otf 
it every year, the amounts were too small individually to attract 
notice, but are nevertheless unmistakable, the periods are as 
follows :— 
1866 August 9th to roth, and again 15th to 21st. 
play) 5th ,, 13th, very marked from 9 A.M to midnight 
of 12th. : 
1868 ,,  15th,, 20th, remarkable (see beginning of this 
letter). 
T8609), yy Siath,,.27th. 
187o ,, 12th,, 22nd, marked from 5 P.M. of 17thto4 P.M. 
of 18th. 
IS7T 55 gth ,, roth and 2oth to 21st. 
1872) 43. toth:,.~ 13th: 
1873 ,,  I5th,, 18th, as recorded in this letter. 
It is not easy to believe that earthquake phenomena will recur 
with such regularity, and we must seek another cause depending 
it would seem on the earth’s annual motion, and to a certain ex- 
tent affecting air and ocean alike. 
It would be premature to express a decided opinion without 
further investigation, which I have not had time to make yet, but it 
seems very probable that the August meteor stream through or near 
which the earth passes about 1oth August may be the cause. It 
will be observed that even in the few observations given above 
there are indications of a five-year period ; for the double dis- 
turbance of 1866 is reproduced in 1871, and the great disturbance 
of 1868 is followed by a similar one in 1873. 
Sydney Observatory, Aug. 23 ’ H. C. RussELt 
Periodicity of Rainfall 
I po not altogether agree with Governor Rawson when he 
says, in his interesting letter in NATURE, vol. viii. p. 245, that 
“*the experience of Barbados is opposed to the theory broached by 
Mr. Meldrumand Mr. J. N. Lockyer.” On the contrary, I rather 
think that Mr. Rawson’s figures support the theory. He has 
taken 1846 and 1871 as middle maxima years (in my first paper 
I also took 1848), whereas 1849 and 1872 are probably more 
correct. Making this slight alteration, we get, according to 
Mr. Rawson’s statistics :— 
Years. Rain. Sums. 
In. In. 
_ | 1843 45°31 ) 
Min. 4 1844 74°45 163 °67 
l 1845 43°91 j 
\ 1848 63°77 ) 
Max. { 1849 52°77 184°42 
| 1350 67°88 | 
§ 1855 77°31 
Min. 31856 ... 48°49 cen ol BORE 
( LBS 7. pees 60°90 
