1890.] NEW YORK ACADEMY OF SCIENCES. 113 



feet above the sea, — at 6.30 a.m., 33°. (In February, 1874, 

 Rohlf noted in the Libyan tlesert a minimum temperature of 

 23°.) 



In considering tlie pliysiological effects of these temperatures 

 one must remember the extreme dryness of tlie atmosphere in 

 tlie desert. 



Rainfall. — My first experience in Egypt was calculated to 

 give the impression that it is a rainy country, for I saw two 

 showers in three days. In passing tlirough the Suez Canal 

 (January 31st), a heavy shower, lasting half an hour, drove the 

 passengers to shelter, and a brilliant rainbow delighted beholders. 

 Two days later, rain again fell at night in Cairo, making the 

 dirty streets more nasty still. Of course this experience was 

 exceptional, as rain is a rarity in Cairo. Authorities give the 

 rainfall at Alexandria as about 8 inches per annum, and at Cairo 

 about 1.2 inches; while in Upper Egypt the precipitation of 

 moisture is far less : there are adults living there who say they 

 have never seen rain. 



I noticed, on the other hand, unmistakable signs of recent 

 rains, such as dried mud-puddles, raindrop-prints, etc., at 

 several points, near Cairo, east of Tliebes (Wadi Bab-el-Molook), 

 and in the peninsula of Sinai, and I was impressed with the 

 belief that more rain falls in Egypt than is usually supposed. 

 A local shower passing over a sandy, gravelly region, makes but 

 little impress on it ; and there is no corps of trained observers, 

 outside of Cairo and Alexandria, to record the phenomenon. 

 On visiting the Khedivial Astronomical Observatory just out of 

 Cairo, I was cordially received by the Director, Mr. T. Esmatt, 

 a graduate of the Ecole Polytechnique of Paris, and for three 

 years an assistant in the Naval Observatory at Washington. I 

 take pleasure in mentioning his politeness and courtesy, but 

 cannot omit pointing out a weakness; he took me to the roof of 

 the building to see the meteorological instruments, and I noted 

 that the rain-gauge was quite full of water ; this again gave me 

 reason to regard Egypt as a rainy country. (The last shower 

 fell one month previously.) 



Being on the lookout for signs of water in the desert of Sinai, 

 I made the following notes : — The slight depressions in broad 

 plains and the deep, narrow valleys in the hill country, both in- 

 discriminately called wadis, present the appearance of dried-u]i 

 water-courses ; the signs are unmistakable, — a tortuous channel 

 with vertical sides carved out of the gravelly bottom, pebbles 

 and boulders transported from distant sources scattered over the 

 surface, mud-flakes and mud-cracks in small bays, as it were, at 

 the sides of the main channels. At two or three places on the 

 sea-coast, extensive mud-flats were pitted with characteristic rain- 



