4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL.98 



cost or attention. While on Mount Wilson, several years ago, I 

 bought 200 feet of black garden hose. I coiled 150 feet of it in a 

 flat coil upon a wooden X, and carried it up the ladder to the south 

 side of the cottage roof. The other 50 feet I connected to the water 

 hydrant in the yard and to a spigot in the bathtub. By this simple 

 arrangement we could draw 5 gallons of very hot water each half 

 hour on every sunny day. 



SOLAR COOKERS 



When we attempt cooking by sun heating we require temperatures 

 far above the boiling point of water. Hence some other liquid of a 

 much higher boiling point is desirable as a heat conveyor, otherwise 

 high pressures and evaporation would be met with. In our cooker on 

 Mount Wilson I used engine cylinder oil within a blackened metal 

 tube in the focus of the mirror. About 60 gallons of this oil were 

 employed in the system, so that there was a large capacity for heat, 

 and cooking could be done by night as well as by day. However, it 

 required about 2 days of sun to get the system heated initially, for 

 owing to nearby trees there were only 7 hours per clay of sunshine. 

 In recent installations I have preferred to use "Arochlor," a nearly 

 black liquid product of the Monsanto Chemical Company. I have 

 made this liquid almost completely absorptive of sun-rays by adding 

 a small amount of lampblack in suspension therein. While engine 

 cylinder oil chars somewhat, and evaporates considerably at 210° C, 

 "Arochlor" does not boil below 350 C, and evaporates scarcely any 

 at lower temperatures. This liquid, being highly absorptive, may be 

 used directly in the vacuum-jacketed glass focus tube. Circulation 

 may be provided by bringing back from the oven sheath a small metal 

 or glass tube within the focus tube to near its lower end. Such a 

 focus tube passes freely through the hollow trunnion at the upper 

 end of the mirror, and is sealed by a well-designed stuffing box to 

 the metal sheath which encloses the oven. According as one wishes 

 for a quickly heating oven, or on the other hand for one to remain 

 hot through temporary cloudiness and the night hours, the oven 

 sheath contains little or much of the liquid. This part of the system 

 may be surrounded by a thick layer of glass wool for insulation, 

 leaving, of course, means for reaching the oven door. 



In another embodiment of the cooking device, I have sealed the 

 glass vacuum-jacketed focus tube to a vertical cylindrical glass jar 

 to contain the liquid. Within the liquid is an inner glass jar used as 

 the oven. The oven is approached from above with food to be cooked. 



