42 



ASTRONOMICAL PHENOMENA AND PROGRESS. 



Pinkish Color of the Sun. Nature received 

 several communications during the year from 

 correspondents, describing a pinkish color of 

 the sun, which they had noticed. Mr. A. S. 

 Herschel, who was favored with a sight of the 

 phenomenon, at Cranbrook, England, May 23d, 

 says: 



The sun presented a round disk of a very unusual 

 pinkish color, here and at Cranbrook (about five 

 miles northeast from Hawkhurst), in Kent, between 

 five and six o'clock p. M. on the afternoon of Mon- 

 day, the 23d ult. It was so seen by myself at Cran- 

 brook, in company with several others, who thought 

 that the color was quite unusual, shining through a 

 thick haze of apparently low cirrpstratus, but which 

 was perhaps rain-cloud, as the air at the time was 

 light from the north, and cold, while the mist, or 

 haze, seemed to be at no very great elevation above 

 the ground, and considerably Tower than those or- 

 dinary forms of cirrostratus in which halos and 

 mock-suns are generally seen. 



The color observed here was a pinkish buff, or 

 such a mixture of pink and yellow as to suggest the 

 abundance of more blue and violet, and the absence 

 of more yellow light than in the orange and reddish 

 tints, generally seen in the setting sun, so as to re- 

 semble the color of very pale blotting-paper, or a 

 light flesh-color. While the disk was still clearly 

 seen of this color, two or three sun-spots were visi- 

 ble upon it with the naked eye. These could no 

 longer be distinguished at six o'clock, when the pe- 

 culiar pinkish hue was was also succeeded by the 

 ordinary yellow of the sun's disk near the horizon, 

 seen through a thick haze. On the same afternoon 

 (of the 23d) the appearance of the sun's round disk 

 through a thick cloud of haze in the sky was noticed, 

 for a considerable time, as visible with rare and 

 unusual distinctness at Tunbridge Wells, in Kent. 



Another correspondent speaks of a similar 

 appearance of the sun ohserved at Rohrback, 

 on the Moselle, May 23d. The day had been 

 warm, without wind. Soon after 2 r. M. the 

 horizon became charged with mist, and rain 

 threatened. About 3 o'clock, the sun lost its 

 brilliancy, assumed a pale-yellow hue, and 

 might have been taken for the moon but for 

 its diameter. A mist then began to rise, and 

 a north wind to blow, and at 4 o'clock the 

 sun became rose-colored, and soon after scar- 

 let. In this case, as in that described by Mr. 

 Herschel, the hazy state of the atmosphere 

 was supposed to be one cause of the phe- 

 nomenon. 



Utilizing the /Sun's Heat for Motive Power. 

 A Solar Engine. Captain John Ericsson, the 

 distinguished inventor of the caloric-engine, 

 contributed during the year a series of re- 

 markable original papers to the London Engi- 

 neering Journal, descriptive of his long and 

 thorough investigations into the dynamic value 

 of the sun's heat for mechanical work, and of 

 his method of utilizing it by means of a solar 

 engine. He omits to give plans and a detailed 

 account of the mechanism by which the sun's 

 radiant heat is concentrated, in order to " pre- 

 vent enterprising persons from procuring pat- 

 ents for modifications," experience having 

 taught him the danger of early publications of 

 that kind. He declares, however, that he 

 does not intend to take out a patent for his in- 

 vention, and purposes to devote the remainder 



of his life to its perfection, and says that with- 

 in a few years the entire engineering commu- 

 nity of both hemispheres will be invited to 

 take the matter in hand. The following are 

 the more important parts of his statement of 

 results and of expectations : 



The several experiments that have been made show 

 that the mechanism adopted for concentrating the 

 sun's radiant heat abstracts, on an average, during 

 nine hours a day, for all latitudes between the equa- 

 tor and 45 degrees, fully 3.5 units of heat per minute 

 for each square foot of area presented perpendicularly 

 to the sun's rays. A unit of heat being equivalent to 

 772 foot-pounds, it will be perceived that, theoretical- 

 ly, a dynamic energy of 2,702 foot-pounds is transmit- 

 ted by the radiant heat, per minute, for each square 

 foot ; hence 270.200 foot-pounds for an area of ten feet 

 square. If we divide this sum by the adopted stand- 

 ard of 33,000, we ascertain that one hundred square 

 feet of surface exposed to the solar rays develop con- 

 tinuously 8.2 horse-power during nine hours a day, 

 within the limits of latitude before mentioned. But 

 -engineers are well aware that the whole dynamic en- 

 ergy of heat cannot be utilized in practice by any 

 engine or mechanical combination whatever, nor at 

 all approached ; hence I have assumed, in order not 

 to overrate the capability of the new system, that a 

 solar engine of one-horse power demands the concen- 

 tration of solar heat from an area of ten feet square. 

 On this basis I will now proceed to show that those 

 regions of the earth which suffer from an excess of 

 solar heat will ultimately derive benefits resulting 

 from an unlimited command of motive power which 

 will, to a great extent, compensate for evils hitherto 

 supposed not to be counterbalanced by any good. 

 Before entering on this task of estimating the results 

 of utilizing sun-power, it will be well to scrutinize, 

 as closely as we can, the mechanical devices by 

 means of which we propose to avail ourselves of the 

 fuel contained in that great store-house whence 

 it may be obtained free of cost and transportation. 

 The solar engine, we have seen, is composed of three 

 distinct parts : the engine, the steam generator, and 

 the mechanism by means of which the feeble inten- 

 sity of the sun's rays is augmented to such a degree 

 that the resulting temperature will exce_ed that of the 

 lowest pressure of steam admissible in an efficient 

 engine. As to the motor itself, it suffices to say 

 that it is essentially a modem steam-engine utiliz- 

 ing, to the fullest extent, the mechanical energy of 

 the steam generated by the concentrated solar rays. 

 Eegarding the steam generator, it will only be neces- 

 sary to state that it is not exposed to the action of 

 fire, clinkers, or soot, and therefore can only suffer 

 from the slow action of ordinary oxidation. We 

 have lastly to consider the efficiency of the mechanism 

 by means of which the solar heat is concentrated and 

 the temperature raised above that of the water in the 

 steam generator. Eegarding this mechanism con- 

 centration apparatus it may appropriately be termed 

 it will be asked : Is it costly ? is it heavy and bulky 

 so as to render transportation difficult ? and finally 

 the question will be put, Is it liable to derangement 

 and expensive to keep in order? I will answer these 

 questions in the same order in which they have been 

 presented. The cost is moderate. The weight is 

 small indeed, lightness is the most notable pecu- 

 liarity of the concentration apparatus. As to bulk, 

 this apparatus is composed of small parts readily put 

 together. Eegarding durability, the fact need only 

 be pointed out that certain metals, however thin, if 

 kept dry, may be exposed to the sun's rays during 

 an indefinite length of time without appreciable de- 

 terioration ; hence, unlike the furnaces of steam-boil- 

 ers, which socn become unserviceable, structures 

 protected as the concentration apparatus is, by thin 

 metallic plates, cannot be rendered unserviceable 

 from the mere action of the sun's rays. Another 

 question will be asked, whether the solar engine will 



