August 2, 1 888 J 



NA TURE 



321 



rays," taught me to adopt in place of curved surfaces and 

 converging rays, flat surfaces and parallel rays, as shown 

 by Fig. 2, which represents a transverse section of part of 

 the reflector. The direct vertical solar rays, it will be 

 seen, act on the mirrors ; while the reflected rays, divided 

 into diagonal clusters of parallel rays, act on the heater, 

 the surface of which will thus be exposed to a dense mass 

 of reflected rays, and consequently raised to a temper- 

 ature exceeding 6oo° F. at noon during ordinary 

 sunshine. 



The cost, durability, and mechanical energy of the sun 

 motor being thus disposed of, it remains to be shown 

 whether the developed energy is continuous, or whether 

 the power of the engine changes with the increase and 

 diminution of zenith distance and consequent variation 

 of atmospheric absorption. Evidently an accurate know- 

 edge of the diathermancy of the terrestrial atmosphere 



is indispensable to determine whether the variation 

 of the radiant energy is so great that the develop- 

 ment of constant power becomes impracticable. Of 

 course, manufacture and commerce demand a motor 

 developing full power during a modern working day 

 of eight hours. Observations relating to atmospheric 

 diathermancy continued during a series of years, enable 

 me to assert that the augmentation of solar intensity 

 during the middle of the day is so moderate that by 

 adopting the simple expedient of wasting a certain 

 amount of the superabundant heat generated while the 

 sun is near the meridian (as the steam engineer relieves 

 the excess of pressure by opening the safety-valve) a 

 uniform working power will be developed during the 

 stipulated eight hours. The opening of the safety-valve, 

 however, means waste of coal raised from a great depth 

 at great cost, and possibly transported a long distance, 



while the radiant heat wasted automatically by the sun 

 motor is produced by fuel obtained from an inexhaustible 

 storehouse free of cost and transportation. 



It will be proper to mention that the successful trial of 

 the sun motor described and illustrated in NATURE, vol. 

 xxxi. p. 217, attracted the special attention of landowners 

 on the Pacific coast then in search of power for actuating 

 the machinery needed for irrigating their sun-burnt lands. 

 But the mechanical detail connected with the concen- 

 tration at a single point of the power developed by 

 a series of reflectors was not perfected at the time ; 

 nor was the investigation relating to atmospheric diather- 

 mancy sufficiently advanced to determine with precision 

 the retardation of the radiant heat caused by increased 

 zenith distance. Consequently no contracts for building 

 sun motors could then be entered into, a circumstance 

 which greatly discouraged the enterprising Californian 

 agriculturists prepared to carry out forthwith an extensive 

 system of irrigation. In the meantime a simple methcd 

 of concentrating the power of many reflectors at a given 

 point has been perfected, while the retardation of solar 

 energy caused by increased zenith distance has been 

 accurately determined, and found to be so inconsiderable 

 that it does not interfere with the development of constant 

 solar power during the eight hours called for. 



The new motor being thus perfected, and first-class 

 manufacturing establishments ready to manufacture such 

 machines, owners of the sun-burnt lands on the Pacific 

 coast may now with propriety reconsider their grand 

 scheme of irrigation by means of sun power. 



John Ericsson. 



THE WHITE RACE OF PALESTINE. 



ON the occasion of my first visit to Palestine I was 

 struck by the number of blue-eyed, fair-haired 

 children whom I met with in the towns and villages, 

 more especially in the mountainous parts of the country. 

 At the t me I supposed them to be the descendants of the 

 Crusaders or of the other natives of Northern Europe who 

 found their way to the Holy Land during the Middle 

 Ages. But a new light has recently been thrown on the 

 matter by the ethnological observations made by Mr. 

 Flinders Petrie in Egypt. 



The winter before last Mr. Petrie was commissioned 

 by the British Association to take casts and photographs 

 of the ethnological types represented on the Egyptian 

 monuments, and to note, wherever it was possible, the 

 colour of the skin, eyes, and hair. It was not the first 

 time, however, that notes of the kind had been taken. 

 Some years ago, Osburn, a careful observer, had noticed 

 that in the sculptures of Ramses II. at Abu-Simbel " the 

 Shasu of Kanana " were depicted with blue eyes, and red 

 hair, eyebrows, and beard, and the Amaur with " the eyes 

 blue, the eyebrows and beard red." As " the Shasu of 

 Kanana " lived a little to the south of Hebron, while the 

 Amaur are the Amorites of the Old Testament, it was 

 clear that a population existed in Palestine in the 

 fourteenth century before our era which had all the 

 characteristics of the white race. 



Mr. Petrie's observations have abundantly verified 

 this conclusion. He finds that, on the walls of a Theban 

 tcmb, the chief of Kadesh on the Crontes is painted with 

 a white skin, and light red-brown hair. Kadesh was the 

 southern capital of the Hittites, after their invasion of 

 Syria, but the Egyptian inscriptions describe it as being 

 '' in the land of Amaur"; and that its chief must have 

 been an Amorite is shown by the fact that the Hittites 

 are depicted with yellow or orange skins, their hair being 

 black, and their eyes dark. 



The physiognomy of the Hittites and Amorites, more- 

 over, differed widely. The Egyptian artists agree with 

 the native Hittite monuments in representing the former 



