The maximum temperatures show that the total amount of heat received on the desert, as compared to that received in the climatic provinces nearer the sea, is not only great, but also that the amount is variable on the desert itself, one station receiving much more heat at certain times of the year than another station. The total heat for each station is arrived at by adding up the daily maxima for the midseasonal months, January, April, July, and October, and dividing by the number of years whose records were consulted. The amounts given in table 11 are the averages for three to four years, for three desert stations and for one station in the Tell. TABLE 11.—_Sums of the daily maximum temperatures._ +--------------+----------+--------+-------+----------+ | Station. | January. | April. | July. | October. | +--------------+----------+--------+-------+----------+ | | _°C._ | _°C._ | _°C._ | _°C._ | | Laghouat | 439 | 476 | 1,135 | 668 | | In Salah | 641 | 1,027 | 1,455 | 1,121 | | Ouargla | 570 | 909 | 1,444 | 923 | | Ft. National | 230 | 470 | 697 | 564 | +--------------+----------+--------+-------+----------+ The variation in total heat received at the three desert stations may probably be explained partly at least by their differences in latitude and in elevation above the sea, as well as the different relations they hold to the highlands of the northern portion of the colony. Laghouat lies immediately south of the Saharan Atlas, latitude 33°48′, and at an elevation of 780 meters. Ouargla is approximately 200 miles south of the mountains, latitude 31°55′, and altitude 150 meters. In Salah is in the midst of the western Sahara, latitude 27°17′, and about 300 meters above the sea. Fort National lies in the Tell about 30 miles from the sea, and at an altitude of 916.3 meters. The latitude of Fort National is 36°38′. There are no published records of the soil temperatures of southern Algeria. In the following table is given soil-temperature data taken at Ghardaia by M. Buret. Maximum and minimum standard chemical thermometers were used. They were placed in a horizontal position in fixed tubes which were about 30 cm. in length. Precautions were taken to properly insolate the instruments. The depth was 15 cm. TABLE 12.—_Soil and air temperatures, Ghardaia, July_ 2-11, 1911.