480 
they originally had been thrown up by a volcanic 
eruption. 
Considering next the action of the finest and 
therefore most persistent dust on solar radiation, 
he finds that the “interception of outgoing radia- 
tion is wholly negligible in comparison with the 
interception of incoming solar radiation.” 
Prof. Humphreys now turns his attention to the 
observational evidence of pyrheliometric records, 
such readings being functions of, among other 
things, both the solar atmosphere and_ the 
terrestrial atmosphere. He thus introduces a 
curve showing smoothed values of the annual 
average pyrheliometric values, and compares this 
with sun-spot frequency values (representing solar 
atmospheric changes) and number of volcanic 
eruptions (representing terrestrial atmospheric 
changes). The similarity of the last-mentioned 
with the pyrheliometric curve leads him to write 
as follows: “Hence it appears that the dust in 
our own atmosphere, and not the condition of the 
sun, is the controlling factor in determining the 
magnitudes and times of occurrence of great and 
abrupt changes of insolation intensity at the sur- 
face of the earth.’ 
The action of the dust intercepting at times as 
much as one-fifth of the direct solar radiation 
leads him to inspect earth surface temperature 
values to inquire whether they are below normal 
on such occasions. The pyrheliometric and tem- 
perature curves suggest a relationship, but, as 
he states, ‘the agreement is so far from perfect 
as to force the conclusion that the pyrheliograph 
values constitute only one factor in the determina- 
tion of world temperatures.” A better agreement 
is secured when the combined effect of insolation 
intensity and sun-spot influence is considered. 
The avthor then discusses the temperature 
variations since 1750 as influenced by sun-spots 
and volcanic eruptions, and indicates that the 
disagreement in the curves of temperatures and 
sun-spots is in every important instance simul- 
taneous with violent volcanic eruptions. 
Limitations of space will not permit us to remark 
on his references to the action of carbon dioxide 
in slightly decreasing the temperature or to 
probable great changes in level. Enough perhaps 
has been said to show that Prof. Humphreys, in 
his interesting attempt to show “that volcanic 
dust must have been a factor, possibly a very 
important one, in the production of many, perhaps 
all, past climatic changes . . has restarted a 
topic which will no doubt call for criticisms and 
discussions from many quarters. 
BIOLOGY OF THE LAKE OF TIBERIAS.1 
‘Lae natural history had its students among 
the ancient inhabitants of Palestine is clear 
from the book of the Levitical-law and from the 
biography of King Solomon. But during the first 
century of our era there is nothing to show that 
the study excited the slightest interest in that 
1 A Report on the Biology of the Lake of Tiberias. Series I. 
and Proceedings, Asiatic Society of Bengal (New Series), vol. ix., 
1913. 
Journal 
No. 1, 
NO. 2304, VOL. 92] 
NATURE 
[DECEMBER 25, 1913 
locality. Fishes are mentioned for their economic 
use; mint, anise, and eummin as objects of taxa- 
tion; the stars in the sky and the flowers of the 
field for their superficial beauty; crops are sup- 
posed to spring from dead seeds; pearls of im- 
possible size are made the symbols of celestial 
splendour. It is only in modern times, and even 
now by strangers rather than natives, that a 
striking contrast to this apathy has been brought 
about. If the water of the Jordan is still carried 
westward for religious rites, samples from the 
Sea of Galilee are now collected with equal care 
for chemical analysis; Syrian Entomostraca are 
reared in England from mud out of the pool of 
Gihon at Jerusalem; from the Galilean lake, by the 
use of tow-nets, hand-nets, and special dredges, a 
varied fauna is obtained, such as might have 
excited the interested surprise of Solomon, but 
would probably have been viewed with disgust by 
the ‘Sanhedrim of a later epoch. 
Prof. Théodore Barrois, in his own interesting 
study of the Syrian lakes (1894), explains that the 
scientific exploration of them was begun in 
August, 1847, by Lieutenant Molyneux, R.N. By 
great efforts this officer succeeded in obtaining 
valuable hydrographical details, both in the lake of 
Tiberias and in the Dead Sea, only to succumb 
almost immediately afterwards to the exhausting 
effects of the climate, torrid and unwholesome at 
that season in the valley of the Jordan. In some 
future Dictionary of National Biography his name 
ought surely to find a place. His initial enterprise - 
has been followed by the labours of many eminent 
naturalists. Dr. Annandale’s present contribution 
to the subject was instigated by his desire to trace 
the genera of sponges and some other inverte- 
brates ‘‘characteristic of the fresh waters of India 
and tropical Africa northwards up the Jordan 
valley, should they prove to have a distribution in 
any way similar to that of the Jordan fishes, 
whose African affinities have long been known.” 
He concludes that ‘‘There is no reason to think 
that the sponge-fauna of the Lake of Tiberias is 
closely related to that of any other lake, but its 
affinities lie rather with that of Eastern tropical 
Asia, and possibly with that of the Caspian Sea, 
than with any in Europe and Africa.” 
His investigation of the Galilean fresh-water 
sponges leads Dr. Annandale to divide the 
Spongillide into two subfamilies, the Spongilline, 
in which microscleres are present, and the Pota- 
molepidine, in which microscleres apparently are 
not produced. Of the former subfamily the lake 
of Tiberias provides only one species, the widely 
distributed Ephydatia fluviatilis, var. syriaca, 
Topsent. Of the latter it furnishes four species, 
allotted to two new genera, Cortispongilla barroisi 
(Topsent), only known from this lake, and Nudo- 
spongilla reversa, N. mappa, and N. aster, all 
new. These are described and figured, together 
with other species introduced for the sake of com- 
parison. 
Useful keys are provided for distinguishing the 
Galilean sponges one from the other, and for 
recognising various genera of the Spongillidee. 
