NOVEMBER 1, 1906 | 
INGA TORE, 
~ 
Tue Mira Maximum or 1906.—In No. 4110 of the Astro- 
nomische Nachrichten Prof. Nijland publishes the results 
of his observations of Mira made during the period 
August 24, 1905, to February 24, 1906. The curve aecom- 
panying the paper shows that a sharp maximum occurred 
on January 3, when the star’s magnitude was 3-9. This 
was preceded by a very flat minimum of about the ninth 
magnitude, extending from the commencement of the 
observations until November 9, 1905, and then a steep 
ascent to the maximum. The lowest magnitude, 9-05, 
occurred on September 23, 1905. 
VETEOROLOGY OF THE NILE VALLEY. 
[HE Egyptian Survey Department, constituted some 
years ago, is adding largely and rapidly to our know- 
ledge of the hydrography, geology, and meteorology of 
the Nile basin. The director-general, Captain Lyons, R.E., 
has prepared and issued a monograph dealing very fully 
with the physiography of the Nile basin. In this work, 
which was reviewed in Nature of September 6 (vol. Ixxiv., 
p- 461), he combines the results of former observers and 
investigators with the data accumulated during the past 
ten or twelve years by his department. It is a storehouse 
of information relating to that most remarkable, and until 
recent years most mysterious, of rivers. 
We propose to give a brief statement, based on the 
information contained in the monograph, of the more 
important features of the meteorology of the Nile Valley 
and their relations to the physiography of the whole area. 
The river obtains its supplies from two collecting areas, 
one the equatorial lake plateau (between lat. 5° S. and lat. 
5° N., and long. 28° and 35° E.), and the second the 
Abyssinian mountain and plateau area (between lat. 7° N. 
and 14° N., and long. 35° and 4o° E.). 
The former is the larger catchment basin, and includes 
the Victoria, Albert Edward, and Albert Lakes, which serve 
as reservoirs to store the rainfall of the whole region. 
The Victoria Lake (equal in area to Scotland) is about 
4ooo feet above the sea, and is slightly lower than the 
mean level of the plateau. The ground rises slightly to 
the south and east, and rapidly to the west to the elevated 
peaks of Ruwenzori, which separate it from the rift valley, 
in which are situated the Albert Edward and Albert Lakes 
connected by the Semliki River. The catchment area of 
the Victoria Lake is only of comparatively small extent, 
not more than twice the area of the lake, the level of 
which hence varies very slightly with the season. The 
Victoria Nile, which issues from the north of the lake, is 
precipitated over the Ripon Falls, and thence passes over 
flat, marshy ground to the Choga Lake Swamp, and de- 
scends by a series of rapids, and finally by the Murchison 
Falls, to the lower level of the Albert Lake at its northern 
extremity in lat. 24° N. 
The Albert Edward and Albert Lakes, with their 
tributaries, appear to collect a larger volume of water 
than the Victoria Lake. The Victoria Lake discharges by 
the Victoria Nile a nearly constant amount, averaging 500 
cubic metres per second, and the Albert Lake amounts 
varying between 500 and 1100 cubic metres per second. 
The discharge of the lake system is carried off north- 
wards from the Albert Lake by the Bahr-el-Jebel, or 
Albert Nile, as it is called by Sir William Willcocks. It 
descends rapidly from a level of 2300 feet to 1500 feet at 
Gondokoro (lat. 5° N.), in a narrow channel with numerous 
falls and rapids, and thence to Lake No (lat. 93° N.) 
through an extensive flat and swampy region. It is joined 
at Lake No by the Bahr-el-Gazal, and about eighty miles 
further down stream by the Sobat. The former drains a 
large portion of the Soudan, its head-waters being chiefly 
in the equatorial belt. The Sobat is formed partly by 
drainage from the same belt and partly from the southern 
face of the Abyssinian plateau. 
Between Lake No and Khartoum, the main stream is 
now known as the White Nile. The discharge of this 
river below Lake No varies to a slight extent during the 
year, and averages only 350 cubic metres per second, and 
hence considerably less than the supply passing into the 
1 **The Physiography of the River Nile and its Racin.” By Captain 
H. G. Lyons, R.E., Director-Gereral Fgyptian Survey Department. 
NO. 1931, VOL. 
ae 
#2) 
river from the Albert Lake. The difference the 
loss by evaporation in the extensive swamp region through 
which these streams flow. That of the Sobat is only con- 
siderable during the rainy season, from April to December, 
ranging between 380 cubic metres and 1470 cubic metres 
per second. The White Nile below the junction of the 
Sobat (lat. 93° N.) to Khartoum (lat. 153° N.) receives 
no affluent, and flows in a broad valley as a wide stream 
of moderate velocity. This part of the Nile plays a sub- 
ordinate but important réle with respect to the Nile floods. 
From May to September the flood water brought down by 
the Sobat River is ponded up or held back in this reach of 
the Nile, and hence does not contribute to the Lower 
Nile flood. Captain Lyons states that this action stores 
up an average of about 1500 million cubic metres from the 
Sobat flood, which is supplied to the Nile in October, 
November, and December, thus prolonging the period of 
the Nile flood, and delaying the fall of the Nile to its 
low-water stage. 
The main flood water of the Nile is brought down by 
the Blue Nile and the Atbara from the Abyssinian plateau. 
The rainfall occurs between June and September, and is 
immediately discharged down the hills into the valleys, 
the greatest portion down the Blue Nile, which joins the 
represents 
White Nile (there forming the Nile) at Khartoum. The 
maximum flood of the Blue Nile is about 12,500 cubic 
metres, and of the Atbara 5000 cubic metres, per second. 
The Nile flood proper is hence due solely to rainfall in 
the Abyssinian and adjacent Soudan area. It commences 
in June, and reaches its maximum about the end of August 
or beginning of September. The maximum height of 
the Nile flood, or the total discharge during the flood 
period, may hence be accepted as a measure of the total 
rainfall over that area, just as the variations of the Victoria 
and Albert Lakes represent the seasonal variations of the 
rainfall in their catchment areas. 
The Nile below the junction of the Atbara (lat. 18° N. 
to lat. 34° N.) receives no affluents, and flows in a com- 
paratively narrow valley, over which the flood waters, with 
their rich alluvial contents, are distributed by means of 
a vast system of canals. 
The Nile basin may hence be divided into three areas or 
regions, not differing greatly in breadth from south to 
is 
north. The most southerly the equatorial lake belt 
between lat. 5° S. and 5° N., an intermediate region 
between lat. 5° N. and lat. 18° N. includes the Soudan 
and Abyssinia, and the northerly region comprises the 
lower Nile basin from lat. 18° N. to the Mediterranean in 
lat. 34° N. The low river supply (January to May) is 
chiefly due to discharge from the equatorial lake area, and 
the summer flood supply to discharge from the Abyssinian 
region. 
The following gives a sketch of the more important 
features of the meteorology of the Nile basin, based on 
the important information and data of Captain Lyons’s 
monograph. 
Temperature is remarkably uniform in the equatorial 
lake region. Thus at Entebbe, on the north shore of the 
Victoria Nyanza, it ranges only between a mean of 72°-7 
in January and 70° in July. In the Nile basin north of 
about lat. 5° N. temperature is lowest in January, and 
attains its maximum in May in the southern half of the 
valley south of Khartoum, and in July in Nubia and 
Egypt. The annual range of temperature increases north- 
wards from the equatorial belt to northern Egypt. The 
greater part of the Nile basin is within the tropics, and 
is throughout the whole year characterised by high tempera- 
ture. That portion of it between lat. 15° N. and_ lat. 
18° N. (in which are the meteorological stations of Khar- 
toum, Berber, and Dongola) is the hottest and driest areain 
the Nile basin. It has an elevation of about 1200 feet. To 
the south is the comparatively damp and cooler region of 
the Bahr-el-Gazal, the Albert Nile, and the lake plateau, 
whilst to the north the valley descends slowly to the re- 
latively cool Mediterranean coast. This—the Soudan hot 
area—is one of the hottest regions in the world. The 
following gives a comparison of the mean monthly maxi- 
mum temperature of Berber in that area, and of Jacobabac, 
the hottest station in India, and also of Massawa, on the 
Red Sea, in the same latitude as Berber :— 
