442 THE POPULAR SCIENCE MONTHLY 



a planet. One of the most interesting series of measurements was 

 made on the light reflected from the bright and the dark bands of 

 Jupiter. Both gave practically the same transmission through the 

 water cell, showing that whatever may be the cause of these dark bands, 

 the diminution in brightness is quite non-selective as regards the infra- 

 red. Interesting measurements were made on Saturn and its rings. 

 Measurements on a planetary nebula showed no positive indications of 

 radiations from it. However, from the observations on blue and red 

 stars, it was not expected that definite indications would be obtained 

 of radiations from a nebula. 



In marked contrast with Venus, Jupiter and Saturn, only about 

 ] 5 per cent, of the light reflected from the Moon is transmitted by the 

 water cell. This is attributable to the fact that the Moon having no 

 atmosphere, the surface becomes warm from exposure to the Sun's 

 rays, and in turn radiates heat waves, which are not transmitted by the 

 absorption cell of water. 



In view of the fact that, heretofore, observers were glad to obtain 

 any indication of the radiation from stars and planets, it is of interest 

 to record that in observing the radiation from Venus it was necessary 

 to place a resistance of 50 ohms in series with the galvanometer in order 

 to reduce the sensitivity and thus keep the galvanometer deflection 

 (which amounted to 127 cm.) upon the scale. 



• it 

 lY. The Absolute Value of the Total Eadiation from the Stars 



It is of interest to obtain a rough estimate of the total amount of 

 heat received from a star as compared with the heat received from the 

 sun, which is of the order of 1.9 gram calories per square centimeter 

 per minute. This was accomplished by standardizing the thermocou- 

 ples and galvanometer in terms of radiant power. In this way it was 

 determined that the amount of starlight which caused a deflection of 

 1 mm. = 34 XIO"^* gram calorie per sq. cm. per minute. Or it would 

 take 100,000,000,000,000/34 minutes, {. e., six million years to raise 

 the temperature of 1 gram of water 1° C. The star Polaris is an ex- 

 cellent example. It produced a galvanometer deflection of 6 mm. 

 Hence it would require only one sixth as long to raise the temperature 

 of 1 gram of water 1° C. In other words, assuming that, in the mean- 

 time, all the incoming radiations are absorbed and that no heat is lost 

 by conduction, convection or radiation, then it will require the radia- 

 tions from Polaris to fall upon 1 square centimeter continuously for one 

 million years in order to raise the temperature of 1 gram of water 1° C. 

 In marked contrast with this value, the radiation from the sun which 

 is transmitted by our atmosphere and falls upon an area of 1 sq. cm. 

 of the earth's surface is sufficient to raise the temperature of 1 gram 

 of water 1° C. in about one minute. Moreover, the total radiation 



