Jan. 3, 1884] 



NATURE 



217 



are known to me. I understand that another deep-sea 

 expedition will be made by our enterprising neighbours 

 next summer, being the fourth in consecutive years.' 

 December 21, 1SS3 J. GwYN Jeffreys 



THE SUN MOTOR AND THE SUN'S 

 TEMPERA TURE 



THE annexed illustration (Fig. i) represents a per- 

 spective view of a sun motor constructed by 

 the writer, and put in operation last summer. This 

 mechanical device for utilisins; the sun's radiant heat 



is the result of experiments conducted during a 

 series of twenty years ; a succession of experimental 

 machines of similar general design, but varying in 

 detail, having been built during that period. The leading 

 feature of the sun motor is that of concentrating the 

 radiant heat by means of a rectangular trough having a 

 curved bottom lined on the inside with polished plates so 

 arranged that they reflect the sun's rays towards a cylin- 

 drical heater placed longitudinally above the trough. 

 This heater, it is scarcely necessary to state, contains the 

 acting medium, steam or air, employed to transfer the 

 solar energy to the motor ; the transfer being effected by 



Ericsson's Sun Motor, erected at New York, 18 



means of cylinders provided with pistons and valves re- 

 sembling those of moiive engines of the ordinary type. 

 Practical engineers as well as scientists have demonstrated 

 that solar energy cannot be rendered available for pro- 

 ducing motive power, in consequence of the feeblene s of 

 solar radiation. The great cost of large reflectors and 

 the difficulty of producing accurate curvature on a large 

 scale, besides the great amount of labour called for in 



' PS.— In NatI're of December 20 (p. 172), I overlooked the misprint 

 of India f^r Siveden.— J. G. J. . 



preventing ihe polished surface from becoming tarnished, 

 are objections which have been supposed to render direct 

 solar energy practically useless for producing mechanical 

 power. 



The device under consideration overcomes the stated 

 objections by very simple means, as will be seen by the 

 following description : —The bottom of the rectangular 

 trough consists of straight wooden staves, supported by 

 iron ribs of parabolic curvature secured to the sides of the 

 trough. On these staves the reflecting plates, consistirg 



