No. 3 (I921) SOLAR OVEN 265 



4. Mounting. — The oven — see appended photographs — is then 

 mounted so as to insure receipt of the maximum of direct rays; it 

 is obvious that, to avoid rejfection from the glass surfaces, the sun's 

 rays must always fall as perpendicularly as possible to the glass 

 surface ; hence the oven must be so inclinable as to follow the 

 sun ; moreover it must face the east till noon and then the west. 

 This is effected by fixing it on a pedestal with a simple inclining 

 arrangement of quadrant pattern, so that every hour or less the 

 surface of the oven may be altered to obtain the necessary per- 

 pendicularity of the rays ; moreover the whole pedestal revolves 

 on a circular track so that when, near noon, the oven is nearly 

 horizontal facing east, it is revolved so that it now presents its 

 surface to the west. It is found that little practical effect is 

 obtained much before 9 a.m. ; after 3 p.m. the internal temperature 

 rapidly fall^. 



5. Temperatures obtainable. — Roughly speaking, the temperature 

 obtained with this simple plant — ^without extra reflectors — which 

 was not elaborated or perfected for want of time, resources, and 

 need, is double that of the exterrial direct sun heat ; that is, if a 

 thermometer placed outside in the open sun marks 130° F. the 

 temperature in the oven may be anything from 250° to 280'' F. if 

 the oven is properly made, insulated, and attended to ; 290^ F. was 

 the highest temperature thus obtained in March (vernal equinox) 

 when the outside thermometer marked about 140" F. This, how- 

 ever, was raised to a maximum of 325° F. by a couple of side wings 

 of not very good tin plate. 



6. Uses. — ^The oven has solely been used for stoving lacquered 

 tins'at, say, 250° F. It is obvious that, in its present form, it cannot 

 be used for evaporative or cooking purposes since the steam would 

 not only cloud the glass but could not be removed without 

 destroying the operation of the oven, which develops temperature 

 by trapping heat in a stagnant, unchanged atmosphere. War 

 difficulties prevented developments which were intended and 

 planned out, and which may yet be taken in hand, viz., the perfect- 

 ing of the reflecting arrangements and the raising of steam or at 

 least the boiling of water by means of convolutions of thin copper 

 pipes (blackened) passing through such an oven of increased size ; 

 such a convolution w^ould be fed from a blackened tank placed in 

 the open sun, and surrounded at a few inches distance by a glass 

 frame so that the temperature of the water in the feed tank may 



