Chapter I: Part 1

[Plate A: OUTLINE MAP OF ALGERIA SHOWING MAIN FEATURES OF SURFACE DRAINAGE Compiled by G. Sykes, Esq. F. R. G. S.]

[Plate 1:

Illustration: Fig. 1. View of the Oasis of Laghouat

Illustration: Fig. 2. Wood market at Laghouat. Juniper, oak, pine, and other kinds of wood, each bunch a camel load, exposed for sale.

Illustration: Fig. 3. Wood market at Laghouat. Roots of Zizyphus, branches of juniper and pine, and pine bark. The latter is said to be used for staining.]

BOTANICAL FEATURES
OF THE
ALGERIAN SAHARA

BY
WILLIAM AUSTIN CANNON

WASHINGTON, D.C.
PUBLISHED BY THE CARNEGIE INSTITUTION OF WASHINGTON
1913

CARNEGIE INSTITUTION OF WASHINGTON
PUBLICATION NO. 178

PRESS OF J.B. LIPPINCOTT COMPANY
PHILADELPHIA

CONTENTS.
* * * * *

PAGE
Introduction 1

Geographical Characteristics of Algeria 2

Climate of Algeria 6

Some Characteristics of the Vegetation of the Tell 15

The Forests of Algeria 18

The High Plateau 20

Boghari to Laghouat 20

Djelfa to Laghouat 22

Laghouat 23

The Oasis of Laghouat 24

The Plain 25

The Dunes near Laghouat 27

The Mountains about Laghouat 28

Effects of Grazing on Vegetation near Laghouat 29

From Laghouat to Ghardaia 31

Region of the Dayas 31

Daya of Tilrempt 32

The Chebka 34

Ghardaia 36

The Oasis of Ghardaia 38

The Plain (Hamada) of Ghardaia 39

The Mountains about Ghardaia 41

The Valley of the M’Zab 41

Protected Areas near Ghardaia 42

Root-Habits in the Ghardaia Region 44

Leaf-Habits in the Ghardaia Region 49

Growth and Flowering Habits in the Ghardaia Region 49

Ghardaia to Touggourt 50

Ghardaia to Ouargla—Vegetation 53

Ouargla to Touggourt—Vegetation 56

Touggourt to Biskra—Physical Features and Vegetation 58

The Biskra Region 59

Topography 59

Plant Habitats of the Biskra Region 60

Vegetation of the Biskra Region 61

General Summary and Conclusions 66

The Environmental Conditions of Plants in Arid Regions 66

Environmental Features of the Flora of Algeria 69

Some Effects of Temperature and Rainfall in Southern Algeria 71

The Soil Relation in Southern Algeria 73

Root-Characters and Species Distribution in Southern Algeria 76

The Biotic Factor 77

Comparison of Some General Features of the Vegetation of
Southern Algeria and of Southern Arizona 79

LIST OF ILLUSTRATIONS.
* * * * *

Plate A. Outline map of Algeria, showing main
features of surface drainage.

Pl. 1, fig. 1. View of the oasis of Laghouat.

2. Wood market at Laghouat. Juniper, oak, pine, and
other kinds of wood, each bunch a camel load,
exposed for sale.

3. Wood market at Laghouat. Roots of _Zizyphus_,
branches of juniper and pine, and pine bark.
The latter is said to be used for staining.

Pl. 2, fig. 4. Shoot-habit of _Acanthyllis tragacanthoides_.
Laghouat.

5. Shoot-habit of _Zollikoferia spinosa_. Laghouat.

6. _Acanthyllis tragacanthoides_ on sandy plain.
Laghouat.

7. _Zollikoferia spinosa_ in habitat, plain
(hamada). Laghouat.

Pl. 3, fig. 8. Detail of north slope of Nomad Mountains, where
_Zollikoferia spinosa_ is the dominant species.
Laghouat.

9. Vegetation of plain (hamada) at Tilrempt. The
conspicuous shrub is _Haloxylon articulatum_.

10. The daya of Tilrempt from the plain, showing the
character of the depression.

Pl. 4, fig. 11. Near view of the daya of Tilrempt. The fortified
stage station, bordj, and a nomad camp are to
be seen. The flattened, level, lower surface of
the trees is the effect of grazing, mainly by
camels.

12. Jujube (_Zizyphus_) shrubs and betoum
(_Pistacia_) at the daya of Tilrempt.

Pl. 5, fig. 13. A young specimen of betoum in the midst of a
protecting jujube at the daya of Tilrempt.

14. Leaf and shoot habit of the jujube (_Zizyphus
lotus_). Daya of Tilrempt.

15. Leaves of the betoum (_Pistacia atlantica_) from
the daya of Tilrempt.

Pl. 6, fig. 16. South wall of the valley of the Oued M’Zab at
Ghardaia.

17. Detail of an eroded bank of the Oued M’Zab at
Ghardaia. The overhanging stratum is hardpan
similar to the “caliche” of southwestern United
States.

Pl. 7, fig. 18. Shoot-habit of _Haloxylon articulatum_, from the
plain near the daya of Tilrempt.

19. Agriculture at Ghardaia. The fields are divided
into plots about 3 by 4 feet in size, for the
more economical use of water. Young barley is
shown growing (November).

Pl. 8, fig. 20. Vegetation in upper part of a “draw” on plain
north of the M’Zab Valley, Ghardaia.

21. Situation of square No. 2, on plain north of
valley at Ghardaia.

Pl. 9, fig. 22. _Capparis spinosa_ at base of valley wall at
Ghardaia.

23. Leaves of _Capparis spinosa_ from Ghardaia.

Pl. 10, fig. 24. Leaf-habit of _Dæmia cordata_. Ghardaia.

25. Shoot-habit of _Salvia ægyptica_. Ghardaia.

26. Upper surface of rocks, showing small incrusting
lichens, on a low mountain about 5 km. north
of M’Zab Valley, Ghardaia.

Pl. 11, fig. 27. Habitat of _Peganum harmala_, at Melika, Ghardaia.

28. Shoot and leaf habit of _Peganum harmala_, from
Ghardaia.

Pl. 12, fig. 29. Habit of _Henophyton deserti_ at Ghardaia when
growing in a protected situation (cemetery).

30. Leaf-habit of _Henophyton deserti_. Ghardaia.

Pl. 13, fig. 31. View in a cemetery at Ghardaia, to show the
relatively abundant vegetation.

32. View in an M’Zabite cemetery, Ghardaia.
_Haloxylon articulatum_ is the leading species
shown.

Pl. 14, fig. 33. Habit of _Deverra scoparia_, from plain about 3
km. north of M’Zab Valley, Ghardaia.

34. Root-habit of _Gymnocarpos fruticosum_, from
plain about 3 km. north of M’Zab Valley at
Ghardaia.

Pl. 15, fig. 35. Root-habit of a mature specimen of _Peganum
harmala_, from the floor of the M’Zab Valley
near Ghardaia. The soil at the place is
comparatively deep.

Pl. 15, fig. 36. Root-systems of _Helianthemum sessiliflorum_
(right), _Haloxylon articulatum_, and _Nolletia
chrysocomoides_ (left), from the flood-plain of
the Oued M’Zab, Ghardaia.

Pl. 16, fig. 37. Shoot and root habit of _Citrullus colocynthis_.
Oued M’Zab, Ghardaia.

38. _Euphorbia guyoniana_, in the valley of the Oued
M’Zab at Ghardaia.

Pl. 17, fig. 39. Habit of _Euphorbia guyoniana_. Ghardaia.

40. To the left, shoot of _Centaurea_ sp., showing
effect of grazing; to the right, shoots of
_Teucrium pseudo-chamæpitys_. From Ghardaia.

Pl. 18, fig. 41. Habit of _Salsola_ sp. (below) and _Echinopsilon
muricatus_, from the M’Zab Valley, Ghardaia.

42. Ghardaia to Ouargla. View overlooking the hamada
about 28 km. from Ghardaia. The relatively
abundant vegetation is associated with a
light cover of sand over the area shown. The
leading species are _Aristida_, _Deverra_, and
_Haloxylon_.

Pl. 19, fig. 43. _Retama retam_, in dunes about 58 km. from
Ghardaia.

44. Dates at the Bordj Zolfana, about 58 km. from
Ghardaia—one of two wells encountered between
Ghardaia and Ouargla.

45. Ghardaia to Ouargla. View overlooking flood-plain
of the Oued M’Zab, or a tributary of this oued.
The adjacent upland is apparently without
plant life.

Pl. 20, fig. 46. Vegetation on edge of the Oued M’Zab, about
63 km. east of Ghardaia, showing habitat of
_Rhantherium adpressum_ in foreground.

47. Sandy flood-plain of the Oued M’Zab, about 63
km. from Ghardaia. _Retama_, _Genista_, and
_Ephedra_ are the leading plants in this place.

48. Habit of _Ephedra alata_ in habitat shown in
figure 47. This specimen was 1.5 m. high.

Pl. 21, fig. 49. View of habitat of _Ephedra alenda_, 138 km. from
Ghardaia.

50. Detail of suckering habit of _Ephedra alenda_,
from habitat shown in figure 49.

Pl. 22, fig. 51. Vegetation, mainly _Ephedra_ and _Retama_, of the
western edge of the Chott Mellala.

52. Approach to western edge of the Chott Mellala,
showing characteristic rounded hills, or
mamelons.

Pl. 23, fig. 53. View between the Ouargla plain and the Chott
Mellala, showing characteristic appearance of
eroded hills.

54. Looking toward the Ouargla plain (reg).

55. Shallow well about 25 km. north of Ouargla.

Pl. 24, fig. 56. Ouargla to Touggourt. Leaf-habit of _Limoniastrum
guyonianum_. The surface of the leaves is
covered with an incrustation of salts.

57. Habit of _Limoniastrum guyonianum_. About 25 km.
north of Ouargla.

Pl. 25, fig. 58. Vegetation of the reg desert, about 25 km. north
of Ouargla. _Ephedra_ and _Retama_ are the
leading species of the area—a spreading dune.

59. Shoot-habit of _Halocnemon strobilaceum_. About
28 km. north of Ouargla.

Pl. 26, fig. 60. Habit of _Halocnemon strobilaceum_ on the edge of
a chott, about 28 km. north of Ouargla.

61. Shoot and leaf habit of _Anabasis articulata_,
about 32 km. north of Ouargla.

Pl. 27, fig. 62. Detail of the shoot-habit of _Salsola
tetragona?_, about 25 km. north of Ouargla.

63. Habit of _Nolletia chrysocomoides_ near the edge
of a chott, about 80 km. north of Ouargla.

Pl. 28, fig. 64. _Tamarix_ sp. as a sand-binder near Bled-el-Amar,
south of Touggourt.

65. Biskra. Habitat of _Euphorbia guyoniana_, looking
toward the Djebel Maouya, with the Chaine de
Sfa in the background.

Pl. 29, fig. 66. Characteristic vegetation on the north slope
of the Djebel Bou Rhezal, Biskra. _Haloxylon
scoparium_ is a prominent species.

67. North base of Ed Delouatt hills, west of Biskra,
showing the low facing dunes. To the right is a
glimpse of an oued which pierces the hills in
the middle distance.

Pl. 30, fig. 68. Flood-plain of the Oued Hamman es Salahin,
Biskra. Halophytes of various species occupy
the foreground.

69. Habitat of _Phelyæa violacea_ shown in figure 70.

Pl. 31, fig. 70. Young shoots of _Phelypæa violacea_, at north
base of Ed Delouatt hills, Biskra.

71. Habit of young specimens of _Phelypæa_. Except
for about 15 cm., plants were buried by sand.
Biskra.

Pl. 31, fig. 72. _Asphodelus_ sp. at north base of Ed Delouatt
hills, Biskra. Photographed in March.

Pl. 32, fig. 73. Detail of square No. 1, on low hills north of
Biskra.

74. Vegetation of north slope of the low hills which
are north of Biskra. _Ferula vesceritensis_ is
the perennial appearing in the figure.

Pl. 33, fig. 75. Detail of square No. 2, near area shown in fig.
74. _Ferula_ and _Haloxylon_ are leading
species.

76. Root-habit of _Haloxylon scoparium_, from a wash
near Biskra.

77. Young shoots and mature roots of _Ferula
vesceritensis_. North of Biskra.

Pl. 34, fig. 78. Root-habit of _Fagonia_ growing on edge of a
wash. Biskra.

79. Large lateral root of _Haloxylon_, with numerous
deciduous rootlets, no longer functional.

80. Shoot-habit, taken from above, of _Fagonia_ from
the flood-plain of a small oued near Biskra.

Pl. 35, fig. 81. Spring annuals, March 17, on north slope of the
Djebel Bou Rhezal, Biskra.

82. Root and shoot habit of _Peganum harmala_,
Biskra. The main root is especially well
developed, although the species has a
generalized root-system.

Pl. 36, fig. 83. Annuals growing with _Peganum_, near Biskra.

84. General view of the north face of the Djebel Bou
Rhezal, Biskra. Apparently barren, plants are
rather numerous in the rock crevices and small
washes of the mountains.

BOTANICAL FEATURES OF THE ALGERIAN SAHARA.

* * * * *

=INTRODUCTION.=

The present paper is designed to give the results of some field-work in southern Algeria in the autumn of 1910 and the spring of 1911. The chief purpose of the tour was to examine the more obvious features of the physiological conditions prevalent in the region in question and, in connection with these observations, to make some detailed studies of the root-habits of the most striking species of the native flora. The route lay through the Atlas Mountains, over the High Plateau, and for some distance into the Sahara itself, returning by a somewhat similar way farther to the east. The country traversed was extremely varied in topography and in plant life, and probably the most southern regions seen may be taken as typical of much of the western Sahara. The distance covered in the more arid portions of the colony was about 1,000 miles.

An English-speaking tourist, or any tourist for that matter, is something of a curiosity in southern Algeria. We were said to be the second party of “Englishmen” who had passed over the Ghardaia-Ouargla country in twenty-five years.

Leaving Algiers in October, diligence was taken to Ghardaia, the most important town in southern Algeria and the end of the diligence service. Beyond Ghardaia travel is by camel only. The diligence journey, if made without stop, requires six days, running night and day, except the first day’s run, which is by day only. Pauses in the journey to Ghardaia were made at the leading towns or stage stations (bordj), thus affording opportunity to observe several localities in the High Plateau as well as the portion of the desert just south of the Saharan Atlas. Stop-overs were made thus at Medea, Boghari, Djelfa, Laghouat, and Tilrempt. A fortnight was passed at Ghardaia, where the environs of the city were quite thoroughly explored. As there are no roads between Ghardaia and Ouargla, or between Ouargla and Touggourt, it was necessary to organize a small camel-train, engage a cameleer (sokhrar) and servants, and make special arrangements for the trip. Nine days were required for the portion of the journey to Touggourt via Ouargla. At Touggourt diligence was again taken for Biskra, two days’ journey. The return journey to Algiers from Biskra was broken at Batna for the purpose of visiting the fine forest of cedar (_Cedrus atlantica_) in the mountains not far from the town. When Biskra was revisited, in the spring of 1911, the northern portion of Algeria was crossed on the way from Tunis, this affording an opportunity to observe something of the picturesqueness of the mountainous regions as well as the spring flora.

I wish to take this early opportunity to acknowledge my appreciation of assistance received from different persons during the course of the Algerian study, or as a means of preparing for it. I am especially indebted to Prof. H. J. Hall, of Leland Stanford University, who was my companion in Algeria and whose knowledge of the American deserts made his advice doubly valuable. Dr. Keltie, secretary of the Royal Geographical Society, provided letters and information of much use. Dr. Trabut, government botanist of Algeria, whose acquaintance with the country is extensive, very kindly identified all plants sent him and gave valuable aid in other ways. The map (plate A) was prepared expressly for this study by Mr. Godfrey Sykes.

In a country where travel away from the beaten path is not without discomfort, it is important that the way be made as smooth as possible, not alone for comfort but for personal safety as well, and it is therefore a pleasure to acknowledge the many kindnesses shown by the civil and military authorities of the French colony, as also by the American consul and vice-consul at Algiers.

=GEOGRAPHICAL CHARACTERISTICS OF ALGERIA.=

The French colony of Algeria is of large extent and possesses a highly varied topography and great range in climate. With an all-land connection with the continent of Europe in earlier geologic times, the flora and fauna of this portion of northern Africa are closely allied to the fauna and flora of southern Spain, France, and Italy.

Algeria lies to the south of the Mediterranean Sea, between Tunis to the east and Morocco to the west. The northern portion extends somewhat beyond latitude 37°, or that of southern Spain, southern Greece, and the southern part of Asia Minor. The limit of the colony on the south is indefinite, reaching to about latitude 21°. Thus east and west the extent is about 650 miles, and north and south 1,200 miles.

The most important topographical features of the northern part of Algeria are the several mountain masses which together constitute the Atlas range. Lowest in Tunis, where the Atlas Mountains do not exceed 5,000 feet altitude, they attain their greatest height in Morocco, over 13,000 feet. In Algeria an altitude of about 7,500 feet is reached in the Aurés, Dj. Chelia, and in the Great Kabylies. In the eastern portion of Algeria the mountains extend to the coast, but farther west a narrow strip of lowland separates them from the sea. In the east (in the department of Constantine) they constitute a single general uplift, although made up of several groups, but as one proceeds westward the mountains separate into two ranges, which at the Morocco border are about 125 miles apart. The two ranges have been called by various names, among which are the Great Atlas for the southern range and the Little or Maritime Atlas for the northern one. But it seems best to use the names Atlas of the Sahara or Saharan Atlas and Atlas of the Tell or the Tellian Atlas, names which are self-explanatory. The Tellian Atlas and all territory between this range and the Mediterranean Sea is known as the Tell, or the land of hills. This is the most important part of Algeria from an agricultural standpoint, and furnishes grain and other products. Here also are the most important forests, oak, pine, and cedar. Between the two ranges of the Atlas lies the region of the steppes or plateaus, in this study referred to as the High Plateau, inasmuch as the average altitude is over 3,000 feet. The steppe region is highest in the west and is wedge-shaped, in conformity to the bounding mountains. In the eastern portion it breaks up into mountain valleys. The topography of the High Plateau is monotonous. The surface is gently rolling, and here and there are undrained depressions, or _chotts_, where salts accumulate. In rainy seasons the chotts contain water, but in the arid summers they are dry. The region of the steppes is of no agricultural value, although, as will appear below, the harvesting of the alfa grass, which occupies vast areas, is of considerable importance.

South of the Saharan Atlas lies the desert, comprising about 2,000,000 square miles, the topography of which is extremely varied. For present purposes it is sufficient to say that in the extreme southern portion of the Algerian Sahara, and crossed by the Tropic, there is an extensive highland, the plateau of Idghagh, where an elevation exceeding 5,000 feet is reached. All of the Sahara to the west of this plateau, or to the west of a line drawn north from it, appears to be above sea-level (much of it having an altitude of 1,000 feet), and of greater geological age than that portion of the desert lying to the east. North from the plateau of Idghagh the country gradually descends to the depression of which the great Chott Melghir is a part, a region below the level of the sea. Here extends also one of the longest oueds of the Sahara, the Oued Igharghar, which takes its rise in the plateau of Idghagh and empties in the Chott Melghir, an entire length exceeding 700 miles. In the western part of the Sahara the surface descends to the Atlantic, but in the eastern part it falls away to the Mediterranean.

Turning now to consider the part of southern Algeria with which this study especially deals—lying between Laghouat and Ghardaia, between Ghardaia and Ouargla, and between the latter place and Biskra, all to the south of the Saharan Atlas—we find topographical details which are probably representative of much of the rest of the Great Desert. Laghouat has an elevation of 2,400 feet. It lies on the northern edge of the region of the dayas. This region is characterized by the poor development of its drainage and has a slightly undulating surface with frequent depressions, each the center of an area of rather small extent, from which it receives flood-waters. The dayas differ from the other undrained areas, the chotts, in that they do not contain an excess of salt, owing probably to efficient subdrainage. In the region of the dayas the surface falls away to the south or the southeast until the region of the Chebka is reached, which extends to the territory of the Beni M’Zab. In the Chebka low and flat-topped mountains are so irregularly disposed as to give rise to the name, meaning a net; they are separated by valleys, narrow toward the northern portion of the region, but expanding into small plains as one proceeds towards Ghardaia. Ghardaia, the country of the Beni M’Zab, marks the southern limit of the Chebka. At Ghardaia the altitude is 1,600 feet. Between Ghardaia and Ouargla are undulating stony plains, the Gantara (_hamada_), large salt spots, the chotts, and a prominent range of sand mountains, _areg_ desert, possibly 1,000 feet high. At the eastern edge of the Gantara the general level of the country drops suddenly about 200 feet to the Ouargla plain (_reg_ desert), with an altitude less than 500 feet; this is an eroded flood-plain of the Oued Igharghar or its tributaries.

There are no navigable rivers in Algeria. The most important river is the Chelif, which takes its origin in the Saharan Atlas, crosses the High Plateau, breaks through the Atlas of the Tell, and, turning westward, traverses obliquely the Tell for a distance of about 108 miles before discharging into the sea. The Chelif is the only stream which rises in the Saharan Atlas and pierces the northern range. To the south of the Saharan Atlas are several important oueds. One, the Oued Djedi, rises near Aflou and goes easterly, past Laghouat, until it reaches the Chott Melrir, south of Biskra; two others, the M’Zab and the Nessa, drain the region of the Chebka, and taking an easterly or a southeasterly direction reach the Oued Rirh or its upper extension. The Oued Rirh constitutes the northern portion of the great Oued Igharghar, or a tributary of this oued, and extends about 60 miles north from Touggourt to the Chott Merouan. The region of the Oued Rirh is of great economic importance from the production of dates, made possible through the development of artesian wells by the French government. The oueds as a whole are very like the arroyos of the southwestern portion of the United States, in that they carry water for a small portion of the year only, when the torrential rains fill them with a muddy, rushing flood.

In the plains adjacent to the oueds, at Ghardaia especially, the natives usually dig their wells, from which water for domestic as well as for irrigating purposes is obtained. The flood-water of the oueds is also diverted into ditches, or impounded for later use, although the latter has not met with uniform success. The depths at which water has been found vary greatly. At Ouargla the water lies within 3 feet of the surface, although there are also very deep artesian wells, and at Ghardaia it varies from 10 to 50 feet or more. At the daya of Tilrempt the water in the deepest wells stands as deep as 300 feet; it is drawn in a very primitive fashion for purposes of watering flocks and for the bordj. The heaviest vegetation is to be found along the oueds and the nearby flood-plains. Here the water relations are the most favorable and the oueds constitute highways along which plants venture into the desert from the more humid regions.

Very little study appears to have been given the soils of Algeria. It has been stated that there are vast areas of light, sandy soils, and also extensive tracts of marls, clays, and alluvial soils.[1] Gypsum is an important element in the soils, both those of the oases and probably of the open desert also; it occurs in great quantity in the large chotts of the desert, along with common salt and other salts. In the soils of the oases it acts as a cementing material, “uniting the finer soil-grains into aggregates which give the soil a much more sandy appearance than would be suspected from the results of mechanical analysis.” At Laghouat and at Ghardaia a light-colored, hard substance, closely resembling the “caliche” of the southwestern United States, was seen incrusting stones, filling cracks in rocks and crevices between rocks, and in places forming a stratum, horizontally placed (15 cm. more or less in thickness) underneath the superficial soils. This is extremely hard and can be broken or cut with difficulty. In the valley of the M’Zab, where it constitutes a heavy substratum, it appears to be impervious to water. This hardpan is used as threshing floors by removing the superficial soils.

An unexpectedly small amount of sand was observed over the route traversed. Near the southern edge of the High Plateau a sand belt was encountered and a long stretch of low dunes was seen leading to the eastward, which were said to reach nearly to Bou Saada; and again at Laghouat there are dunes to the east of town as well as to the west. Low dunes were seen in the valley of the Oued M’Zab, and sand mountains, possibly 250 meters high, were passed on the way from Ghardaia to Ouargla. Between Ouargla and Touggourt, also, sand was encountered and the way lay across about 12 miles of low dunes; to the north of Touggourt dunes are also to be seen; and finally, some sand is to be found in the neighborhood of Biskra. Although, thus, relatively little sand was met, much of the entire portion of southern Algeria is covered by sand. Large areas of sand-covered country lie to the east of the Oued Rirh, and especially southeast of Touggourt, and also to the west of Ghardaia there is said to be a large dune-covered territory. For the most part, however, the surface of the plains crossed is covered with large or small stones, mingled with which, or beneath which, there is a rather fine clay-like soil. This constitutes the hamada, or stony desert, of which the largest portion of the surface of the Sahara is probably composed. Where stones are largely absent and the soil is fine, usually of fluvian origin, the formation is known as “reg.” Reg desert was encountered at and north of Ouargla, in the drainage of the Igharghar or its tributaries, and south of Biskra. The latter may not, strictly speaking, be reg, but a wide-stretching bajada, and the soil is probably only in small part deposited by rivers.

=CLIMATE OF ALGERIA.=

The climate of Algeria is mild and temperate. This is due to several factors, among which are its situation relative to the Mediterranean on the north and to the Atlantic on the west, as well as to the great desert which constitutes its southern portion, the great variation in topography, and the fairly low latitude. Taking the colony as a whole, there is a great range in temperature, precipitation, relative humidity, and evaporation, to mention only such climatic features as have been reduced and are recorded; and the range in the intensity and in the quality of the light must also be great. The climate of the northern portion of Algeria is coastal, while that of the southern portion is continental.

The distribution in time and in space and the amount of precipitation are of the greatest importance as climatic features of Algeria. The rainfall is heaviest on the littoral, and especially heavy in the eastern portion of the littoral. An average of 1,000 mm. is reported from the immediate vicinity of the sea,[2] and as one goes southward the amount of precipitation rapidly becomes less. In the Tell the average rainfall is 570 mm., while on the High Plateau it is 310 mm. On the desert the rainfall is uncertain both in amount and in time, except that when rains occur the time coincides with the rainy season of northern Algeria. At Biskra the annual precipitation is 199 mm., at Laghouat it is 198 mm., at Ghardaia it is 114 mm., and at El Golea it is 47 mm. In many places in the western Sahara, five years or more go by without fall of rain.

The differences in the geographical distribution of precipitation vary from year to year, as may be illustrated by referring to that for the year 1908, which may be compared with the normal usual distribution as given above. In the northern portion of the country more rain than usual was reported; for example, there was over 1,000 mm. on the littoral east of Algiers, and over 500 mm. on the High Plateau, but on the desert the amount was somewhat less. At Laghouat it was 161 mm., at Ghardaia it was 89.2 mm., and at Ouargla it was 28 mm.

Besides the differences in amount of yearly rainfall, well-marked seasonal amounts of precipitation are also to be noted. In the northern portion of the colony rains are likely to occur in winter and spring, the summer and early autumn being dry; and as one goes south of the Saharan Atlas nearly the same conditions obtain; that is, the rains usually fall during the rainy season of the coast. The seasonal distribution of rain for the Tell, including the stations of the littoral, the High Plateau, the Saharan Atlas, and the desert, for a series of years including 1908, is given in table 1.

TABLE 1.—_Seasonal distribution of rain._

+-------+-----+------------+-------+------+-----------------------+
| |Tell | High |Saharan|Desert| |
|Season.|(10).|Plateau (8).| Atlas | (6).| Remarks. |
| | | | (10). | | |
+-------+-----+------------+-------+------+-----------------------+
| |_mm._| _mm._ | _mm._ | _mm._| |
| | | | | | |
|Winter |469.9|119.3 (50.8)| 113.5| 37.4| The Tell is |
| | | | | | represented by Fort |
|Spring |300.0| 80.5 (95.0)| 88.2| 39.0| National; the High |
| | | | | | Plateau by Geryville |
|Summer | 38.1| 66.5 (35.8)| 50.4| 3.7| (with Ain Sefra, |
| | | | | | for 6 years, in |
|Autumn |287.2|139.5 (58.5)| 123.1| 19.6| parentheses); the |
| | | | | | Saharan Atlas by |
| | | | | | Djelfa; the desert by |
| | | | | | Ouargla. The number |
| | | | | | of yearly records on |
| | | | | | which averages are |
| | | | | | computed are given |
| | | | | | at the head of each |
| | | | | | column in parentheses.|
+-------+-----+------------+-------+------+-----------------------+

The seasonal percentages of precipitation give a more graphic conception of the rainfall conditions for the four physiographic provinces. In the Tell this percentage in winter is 42, in spring 27, in summer 4, and in autumn 27. On the High Plateau the percentages are 30, 20, 16, and 34 for the four seasons respectively. In the Saharan Atlas 30 per cent of the rain occurs in winter, 24 in spring, 13 in summer, and 33 in autumn. In the desert the percentages of rainfall are 37, 39, 4, and 20[3] for the four seasons.

It is of interest also to note the number of days on which the rain fell on an average each year over a period running from 7 to 12 years. Thus at two typical stations on the Tell rain was reported on 102 and 118 days; at two stations on the High Plateau it rained 65 and 83.8 days; at a station in the Saharan Atlas rain was reported on 70 days; at desert stations, at Ouargla rain fell on an average 14.2, and at Laghouat 49 days each year. As a comparison, it may be mentioned that for ten years at Wady Halfi, Egyptian Sudan, there were only 22 days on which rain-drops were seen to fall. (Engler, _loc. cit._)

The amount of precipitation varies greatly for the different desert stations, usually becoming less as one goes south from the High Plateau. As has already been mentioned, the average rainfall at Laghouat, which lies at the southern base of the Saharan Atlas, is 198 mm., the average at Ghardaia is 114 mm., while that at El Golea is 47 mm. The latter station is about 225 miles south of Laghouat, in the midst of the Sahara. The amount of rainfall, however, is greatly influenced by altitude, although lack of adequate precipitation data for the desert makes impossible a detailed presentation of this phase of the subject. As the amount of the yearly precipitation is less in the extreme southern part of Algeria than it is nearer the Saharan Atlas, where the altitude also is greater, it might be expected that the number of rainy days would vary in a like manner. Such records as are at hand, however, do not show this to be the case. For instance, at Ouargla rain falls on an average 14.2 days, average of 7 years, while the rainfall is 90.2 mm.; yet at El Golea, with a rainfall of 47 mm., there are 23.4 rainy days each year.[4]

On the desert the rains are often of a torrential nature, as facts presented above would indicate, and sometimes as much rain falls within a few hours, or even a few minutes, as usually occurs in an entire year. How much of the annual precipitation is of this character and how much is of the non-torrential kind the usual summaries leave entirely out of the account. It is well known that the former type of storm is more destructive and less useful to plants than the latter type. To illustrate the irregularity of the rainfall in the northern Sahara the monthly precipitation at Ouargla for several years is presented in table 2.

TABLE 2.—_Rainfall at Ouargla, in millimeters._

+----+-----+-------+----+----+----+-----+----+
| | |No. of | | | | | |
|Year| Amt.| days |Jan.|Feb.|Mar.| Apr.|May |
| | | rain | | | | | |
+----+-----+-------+----+----+----+-----+----+
|1900| | 1 | | | | | |
| | | | | | | | |
|1901| | 18 | | | | | |
| | | | | | | | |
|1902| 70.5| 8 | | |11.3| | |
| | | | | | | | |
|1903|135.6| 14 |55.0| | | | |
| | | | | | | | |
|1904| 35.0| 26 |20.0| | | | |
| | | | | | | | |
|1905| | | | | | | |
| | | | | | | | |
|1906| | |15.0| | 2.0| 4.0| |
| | | | | | | | |
|1907|210.0| 18 | |68.2| 67|325.0|16.2|
+----+-----+-------+----+----+----+-----+----+
[**Continued]

+----+----+----+----+-----+----+----+----+
| | | | | | | | |
|Year|June|July|Aug.|Sept.|Oct.|Nov.|Dec.|
| | | | | | | | |
+----+----+----+----+-----+----+----+----+
|1900| | | | | | | |
| | | | | | | | |
|1901| | | | | | | |
| | | | | | | | |
|1902| | | 1.8| |46.4|11.0| |
| | | | | | | | |
|1903| | | | | |30.6|50.0|
| | | | | | | | |
|1904| | | | | 9.0| 4.0| 2.0|
| | | | | | | | |
|1905| | | | | | | |
| | | | | | | | |
|1906| | 4.0|80.0| 41.0|80.0| | |
| | | | | | | | |
|1907|20.0| | | 5.0| 3.3| 3.8| 1.3|
+----+----+----+----+-----+----+----+----+

The seasonal distribution of rainfall at four desert stations shows also marked irregularities. The distribution (in percentages) is given in table 3.

TABLE 3.—_Seasonal distribution, in percentages, of rain._

+----------+---------+---------+---------+---------+
| Station. | Winter. | Spring. | Summer. | Autumn. |
+----------+---------+---------+---------+---------+
|Ouargla | 37 | 39 | 4 | 20 |
|Laghouat | 11 | 27 | 31 | 31 |
|Ghardaia | 15 | 23 | 13 | 49 |
|Touggourt | 13 | 30 | 3 | 53 |
+----------+---------+---------+---------+---------+

The relative humidity at the desert stations is often very low, sometimes running in midsummer between 7 and 9 per cent for 6 days, and occasionally being too low to measure with the instruments employed. The mean relative humidity (table 4) shows the general very dry condition of the air of the desert as contrasted with a station in the Tell, and also indicates something of the monthly variations in this factor experienced among the desert stations themselves. The averages given are from 4 to 8 years, except the mean annual for In Salah, which is for 2 years only.

TABLE 4.—_Mean relative humidity, in percentages._

+--------------+------+------+------+------+------+------+------+
| Station. | Jan. | Feb. | Mar. | Apr. | May | June | July |
+--------------+------+------+------+------+------+------+------+
| Ouargla | 61.0 | 58.6 | 60.3 | 51.2 | 52.0 | 49.0 | 44.1 |
| El Golea | 60.8 | 56.8 | 41.3 | 41.3 | 41.0 | 31.3 | 28.5 |
| In Salah | 51.5 | 48.0 | 45.5 | 40.4 | 34.6 | 32.0 | 23.4 |
| Ft. National | 87.4 | 80.3 | 87.6 | 86.6 | 96.6 | 80.4 | 75.8 |
+--------------+------+------+------+------+------+------+------+
[**Continued]

+--------------+------+-------+------+------+------+-------+
| Station. | Aug. | Sept. | Oct. | Nov. | Dec. | Year. |
+--------------+------+-------+------+------+------+-------+
| Ouargla | 44.7 | 50.7 | 56.8 | 59.1 | 52.7 | 54.6 |
| El Golea | 31.8 | 34.8 | 37.1 | 58.1 | 65.1 | 45.5 |
| In Salah | 24.6 | 17.2 | 38.0 | 52.2 | 58.7 | 42.6 |
| Ft. National | 62.8 | 80.2 | 87.7 | 92.8 | 88.4 | 85.1 |
+--------------+------+-------+------+------+------+-------+

A consideration of the evaporation statistics of Algeria for the year 1908 shows some interesting relations. It has already been observed that the rainfall along the coast is less in the west than in the east, and it will appear below that as a rule the temperature of the western portion is lower than that of the corresponding regions lying to the east. In both rainfall and temperature, however, the greatest variation is to be found as one goes inland, when decreasing rainfall and higher temperatures are encountered. A similar relation obtains in evaporation, which becomes continuously greater as the distance from the coast increases; that is, the average evaporation for stations on the High Plateau is greater than for stations in the Tell, and the evaporation at desert stations is greater than the evaporation on the High Plateau. The total average evaporation for the year, in millimeters, for 5 stations on the littoral, was 1,365.3; for 7 stations in the Tell it was 1,378.6; for 4 stations on the High Plateau 2,352.2, and for 3 stations in the desert, 3,977.5. The least evaporation reported was at Bouzarea, which was 989.9 mm., and the greatest was at Ghardaia, 5,309.7 mm.[5]

Table 5 gives in detail the monthly as well as the total evaporation for the year at three desert stations and at Algiers for 1908.

TABLE 5.—_Evaporation in millimeters_, 1908.

+---------+-----+-----+-----+-----+-----+-----+-----+
|Station. |Jan. |Feb. |Mar. |Apr. |May |June |July |
+---------+-----+-----+-----+-----+-----+-----+-----+
|Laghouat |88.9 |102.3|143.4|203.1|289.2|373.9|421.2|
|Ghardaia |172.4|233.4|340.7|528.7|611.7|699.1|749.2|
|Touggourt| |163.9|240.5|274.3|385.2|459.4|565.8|
|Algiers |84.2 |96.8 |90.5 |118.3|151.8|158.6|175.0|
+---------+-----+-----+-----+-----+-----+-----+-----+
[**Continued]

+---------+-----+-----+-----+-----+-----+-----+
|Station. |Aug. |Sept.|Oct. |Nov. |Dec. |Year.|
+---------+-----+-----+-----+-----+-----+-----+
|Laghouat |379.6|264.8|173.9|153.8|159.2|2753 |
|Ghardaia |693.0|468.8|329.4|257.7|225.5|5309 |
|Touggourt|487.3|329.4|222.6|166.1|142.3| |
|Algiers |205.0|165.5|129.0|136.1|143.2|1654 |
+---------+-----+-----+-----+-----+-----+-----+

For a better personal appreciation of the rate of evaporation, as well as for the purpose of comparison, I arranged an apparatus to tell the water-loss from a free water-surface. It was also desirable to determine the relative evaporation of the day and night. As employed, the apparatus consisted of a flat tin dish, with parallel sides, 10 cm. in diameter. To the side was attached, by means of a rubber stopper, a bent glass tube of small diameter. The water-loss was read on this tube. Observations were made at Laghouat and at Ghardaia. Following is a summary of the results obtained at Ghardaia: For a period of 7 days, after November 10, the daily water-loss between 7 a.m. and 7 p.m. was as follows: 5, 8, 8.5, 10.5, 13, 9, and 7.5 mm. The evaporation between 7 p.m. and 7 a.m. was so slight, 1 mm. more or less, that it could not be well determined by the apparatus used.

A good idea of the intensely arid character of the Algerian climate, taken as a whole, is to be obtained by a study of the relation between the total rainfall and the total evaporation, based on the official climatic reports. In tables 6 and 7 the report for the year 1908 is used. The figures represent the ratio (_e_/_r_) between evaporation and rainfall, in which the amount of evaporation is used as the numerator and the amount of precipitation as the denominator. In the monthly evaporation-rainfall table (table 6), in all cases where no rainfall was reported for the month it was called 1 mm. In table 7, however, which gives the seasonal evaporation-rainfall ratio, the actual figures of the government report were in all cases employed, since there was no season during the year 1908, even in southern Algeria, when no precipitation occurred.[6]

TABLE 6.—_Evaporation-rainfall ratio, monthly_, 1908.

+----------------+------+-------+-------+-------+-------+-------+
| Station. | Jan. | Feb. | Mar. | Apr. | May. | June. |
+----------------+------+-------+-------+-------+-------+-------+
| Nemours | 1.07| 1.3 | 1.39 | 1.9 | 131 | 5.4 |
| Cape Falcon | 1.5 | 1.8 | 1.46 | 16.0 | 8.8 | 10.3 |
| Oran | 1.3 | 1.9 | 1.6 | 1.3 | 17.4 | 8.5 |
| Algiers | 0.63| 1.3 | 0.5 | 1.1 | 22.3 | 11.7 |
| Bouzarea | 0.57| 0.67| 0.22 | 0.56 | 8.3 | 4.8 |
| Maison-Carée | 0.72| 0.64| 0.55 | 1.1 | 13.5 | 11.8 |
| Ft. National | 0.72| 0.29| 0.34 | 0.58 | 3.7 | 192 |
| Sidi-bel-Abbès | 0.63| 0.76| 0.6 | 1.1 | 18.8 | 18.5 |
| Saida | 0.67| 0.64| 0.36 | 0.83 | 2.2 | 6.9 |
| Batna | 1.6 | 2.3 | 1.5 | 2.5 | 46.5 | 33.4 |
| Tebessa | 4.6 | 6.05| 21.2 | 3.9 | 252.0 | 2.8 |
| Bou Saada | 4.05| 5.4 | 12.1 | 2.9 | 6.1 | 165 |
| Barika | 2.4 | 8.7 | 9.9 | 5.0 | 5.03| 270 |
| Ain Sefra | 9.2 | 21.5 | 1.5 | 23.8 | 12.4 | 63.1 |
| Geryville | 6.3 | 1.9 | 2.1 | 23.9 | 2.5 | 16.7 |
| Laghouat | 3.09| 4.7 | 9.8 |203.0 | 7.0 | 373 |
| Ghardaia | 8.9 | 233.0 | 81.4 |529.0 | 38.9 | 699 |
| El Oued | 53.9 | 27.7 | 67.0 |629.0 | 369.0 | 465 |
+----------------+------+-------+-------+-------+-------+-------+
[**Continued]

+----------------+-------+-------+-------+------+-------+-------+
| Station. | July. | Aug. | Sept. | Oct. | Nov. | Dec. |
+----------------+-------+-------+-------+------+-------+-------+
| Nemours | 23.6 | 43.3 | 8.6 | 3.1 | 10.6 | 5.7 |
| Cape Falcon | 29.7 | 136.0 | 38.1 | 1.9 | 8.9 | 2.2 |
| Oran | 59.0 | 146.0 | 18.0 | 2.45| 3.4 | 4.4 |
| Algiers | 219.0 | 28.8 | 5.07| 1.06| 1.2 | 1.1 |
| Bouzarea | 53.7 | 27.1 | 3.4 | 0.2 | 0.76| 0.5 |
| Maison-Carée | 149.0 | 12.0 | 5.2 | 0.9 | 0.35| 0.51|
| Ft. National | 42.5 | 15.5 | 2.7 | 1.6 | 0.71| 0.16|
| Sidi-bel-Abbès | 77.8 | 37.8 | 14.8 | 1.4 | 1.9 | 0.8 |
| Saida | 86.7 | 12.1 | 4.7 | 5.8 | 1.2 | 0.78|
| Batna | 24.4 | 7.6 | 3.5 | 4.9 | 2.6 | 1.6 |
| Tebessa | 9.8 | 14.8 | 1.1 | 3.9 | 3.5 | 3.7 |
| Bou Saada | 43.5 | 19.5 | 8.3 | 13.9 | 5.6 | 8.3 |
| Barika | 6.1 | 4.1 | 11.4 | 3.7 | 90.6 | 1.3 |
| Ain Sefra | 16.4 | 124.0 | 328.0 | 14.7 | 13.2 | 1.2 |
| Geryville | 22.5 | 23.4 | 3.4 | 2.1 | 4.1 | 3.9 |
| Laghouat | 421.0 | 21.0 | 25.9 | 14.2 | 154.0 | 104.0 |
| Ghardaia | 166.0 | 25.6 | 66.9 | 23.2 | 49.7 | 225.0 |
| El Oued | 509.0 | 482.0 | 68.6 | 46.1 | 215.0 | 123.0 |
+----------------+-------+-------+-------+------+-------+-------+

TABLE 7.—_Evaporation-rainfall ratio, seasonal_, 1908.

+-----------------+---------+---------+---------+---------+--------+
| Station. | Winter. | Spring. | Summer. | Autumn. | Annual.|
+-----------------+---------+---------+---------+---------+--------+
|Littoral: | | | | | |
| Nemours | 2.69 | 44.09 | 24.1 | 7.4 | 3.0 |
| Cape Falcon | 1.83 | 8.75 | 58.6 | 16.3 | 3.7 |
| Oran | 2.54 | 3.7 | 71.0 | 7.95 | 4.2 |
| Algiers | 1.0 | 7.96 | 86.4 | 2.44 | 1.8 |
| Bouzarea | 0.58 | 3.0 | 28.5 | 1.45 | 0.93 |
| Maison-Carée | 0.62 | 5.0 | 117.4 | 1.48 | 1.5 |
|Tell: | | | | | |
| Ft. National | 0.39 | 1.4 | 83.2 | 1.67 | 1.1 |
| Sidi-bel-Abbès| 0.73 | 8.2 | 38.3 | 6.0 | 2.2 |
| Saida | 0.69 | 1.0 | 3.5 | 3.9 | 1.9 |
| Batna | 1.8 | 2.1 | 0.35 | 3.6 | 4.4 |
| Tebessa | 4.7 | 4.05 | 88.2 | 2.8 | 6.0 |
|High Plateau: | | | | | |
| Bou Saada | 5.9 | 7.0 | 76.0 | 9.2 | 11.0 |
| Barika | 4.1 | 6.6 | 93.5 | 35.2 | 12.2 |
| Ain Sefra | 1.4 | 12.5 | 67.9 | 18.5 | 11.1 |
| Geryville | 7.0 | 9.8 | 20.8 | 3.2 | 3.5 |
|Desert: | | | | | |
| Laghouat | 6.0 | 73.2 | 271.6 | 64.6 | 17.0 |
| Ghardaia | 154.9 | 416.3 | 293.7 | 195.9 | 59.7 |
| El Oued | 68.3 | 354.0 | 485.2 | 109.5 | 63.0 |
+-----------------+---------+---------+---------+---------+--------+

When we reduce the evaporation-rainfall ratios of the different physiographic provinces to simple expressions we gain a comprehensive view of this important climatic factor for the colony as a whole. Thus the annual evaporation-rainfall ratios are as follows: the littoral, 2.5; the Tell, 3.5; the High Plateau, 9.4; the desert, 46.5. The relation of these expressions may also be given thus: 1:1.4:3.7:18.6, for the several regions above given, by which we see how rapidly the aridity of the country increases as the desert is entered. The present custom of considering the southern base of the Sahara Atlas as the northern edge of the desert, in place of including the High Plateau, as was done earlier, is thus well grounded.

The temperatures of the air vary greatly for the different regions, and usually the variation is to be directly related to the positions of the stations as regards the coast and the altitude. Along the coast, however, the temperatures vary even if the stations are at approximately the same elevation. The mean annual temperature at Oran is 16.9° C. and at La Calle 17.7° C., while a study of the January temperatures shows that a similar relation holds good for the entire south coast of the Mediterranean, between Oran and Alexandria. Algiers furnishes one exception to this statement, in that the mean annual temperature is 18.1° C. On the High Plateau the mean temperature falls to 12.7° C. (Batna) and 13.5° (Setif). No records appear to have been made for the high mountains of eastern Algeria, although the fact that snow may remain in sheltered places as late as the latter part of July[7] would indicate that the mean temperature at 2,000 meters elevation is much lower than any above given. On the Algerian Sahara the mean annual temperature is usually higher than at any point nearer the coast, but even here there is considerable variation, depending, among other factors, on the altitude of the stations and their relation to the Atlas. The mean temperature is given by Engler as 20.5° C. for Biskra, 21.0° C. for Ghardaia, and 22.2° C. for El Golea. As increased temperature means increased evaporation, we have in this one factor a powerful agent making for aridity, and when this is associated with decreasing rainfall, as one leaves the coast region, its influence as a determinative factor in the environment of plants is thus seen to be of great importance.

The annual variations in the temperature of the air are very considerable throughout the colony and are especially great on the desert and the High Plateau. At Algiers the variation is 40.7° C., at Setif it is 48.2° C., and at Ghardaia it is 47.9° C. An annual absolute variation of 50° C. is not uncommon on the desert, and Engler cites a range of 57.0° C. at Ghardaia.

The daily range of the temperature is also considerable for all stations, but is especially marked in those of the High Plateau and the desert. The daily range as given by Engler for the former is 17.4° C., and for the latter 20.0° C., but the range on the High Plateau may be greater than 17.4° C., especially during the summer months. For example, at Batna, in 1904, a range of 19.4° C. was reported in April, 20.2° C. in June, 21.8° C. in July, and 20.2° C. in December. Except in December, the great ranges in temperature here cited were on days when the sirocco was blowing from the desert; hence, the usual daily range in temperature would be much less. In the Tell, and especially along the coast, the range in temperature recorded for any day is relatively little, although at the time of the sirocco, as well as during the season of drought, the daily range is not inconsiderable. Table 8 gives the maximum daily range for the months of 1904, for two stations, along the coast, including the Tell, and two stations on the High Plateau. The daily range reported for Batna in June, July, and August, 1902, was somewhat larger than the maxima given in table 8. In 1902 the maximum daily ranges in temperature for the three months at Batna were 23.9° C., 25.3° C., and 24.4° C.

TABLE 8.—_Maximum daily range in temperature_, 1904.

+--------------+-------+-------+-------+-------+-------+-------+
| Station. | Jan. | Feb. | Mar. | Apr. | May | June |
+--------------+-------+-------+-------+-------+-------+-------+
| | _°C._ | _°C._ | _°C._ | _°C._ | _°C._ | _°C._ |
| Algiers | 9.0 | 13.0 | 13.0 | 13.6 | 12.7 | 13.0 |
| Ft. National | 10.4 | 13.8 | 13.0 | 12.4 | 13.0 | 12.8 |
| Batna | 11.5 | 15.4 | 16.4 | 19.4 | | 20.2 |
| Saida | 14.0 | 17.0 | 14.0 | 18.0 | 18.0 | 19.0 |
+--------------+-------+-------+-------+-------+-------+-------+
[**Continued]

+--------------+-------+-------+-------+-------+-------+-------+
| Station. | July | Aug. | Sept. | Oct. | Nov. | Dec. |
+--------------+-------+-------+-------+-------+-------+-------+
| | _°C._ | _°C._ | _°C._ | _°C._ | _°C._ | _°C._ |
| Algiers | 15.0 | 15.4 | 11.2 | 14.0 | 10.8 | 10.6 |
| Ft. National | 12.4 | 14.8 | 16.4 | 11.2 | 11.6 | 11.0 |
| Batna | 21.8 | 16.4 | 16.0 | 19.4 | | 20.2 |
| Saida | 19.0 | 18.0 | 18.0 | 14.0 | 13.0 | 13.0 |
+--------------+-------+-------+-------+-------+-------+-------+

The temperature conditions for the year 1908 will serve very well to further illustrate this phase of the climate of Algeria. No freezing temperatures were reported from the coast stations, although at the northern base of the Atlas of the Tell several degrees of frost were recorded. At Blida, for example, the thermometer registered -4.0° C. as the minimum. Away from the littoral at every station whose records were seen the lowest temperatures were zero centigrade, or below. The coldest weather was felt at Aflou, at the north base of the Dj. Amours, of the Saharan Atlas, where -11.0° C. was reported. The summer was warm along the coast and hot in the interior. The records of temperature of 23 stations of the Tell were seen, and of this number, at only 8 was a temperature of 40° C. reached or exceeded. On the other hand, at 44 out of 56 stations on the High Plateau and the desert, the temperatures reported are as great or greater than 40° C. Where temperatures below this figure were recorded the stations were situated in the mountains.