54 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



tion of the planet, this interval of time will be materially 

 larger. At the end of the eclipse, Secchi was able to follow 

 the moon for twenty-five seconds after the close of the actual 

 eclipse. At the end of forty-eight seconds, he states that there 

 was no longer any trace of the moon that it had evidently 

 completely passed the chromosphere. It is interesting to com- 

 pare the result of Secchi's observations, made with the pow- 

 erful assistance of this method of observation, with those 

 obtained by his two assistants, and it appears that the latter 

 first detected the presence of the moon at the beginning of 

 the eclipse from ten to fifteen seconds after the actual con- 

 tact as observed by Secchi. On the other hand, Respighi 

 applied to the same eclipse of the sun the ordinary spectro- 

 scopic method ; that is, without a j^rism in front of the spec- 

 troscope, and without a spectroscopic slit. In this form of 

 the apparatus we see, not the sun's limb, but the chromo- 

 sphere in the shape of concentric rings ; and Respighi had to 

 assume for the moment of contact that in which the colored 

 rings were entirely broken through. His measurements also 

 dift'er considerably from Secchi's; but it appears that Re- 

 spighi has observed the first contact twenty-one seconds ear- 

 lier even than Secchi. It would seem that Respighi's method, 

 however, can not be so exact as that of Secchi, since Re- 

 spighi does not distinctly see the sun's limb. It is, therefore, 

 apparent that this method suggested by Secchi is a decided 

 improvement upon that which has been employed by several 

 spectroscopists during the past five years. 19 C, 1873, 280. 



THE HEAT EADIATED FROM THE MOOJST. 



The Earl of Rosse has made an attempt to determine, by 

 accurate observations, the heat that we receive from the 

 moon. For this purpose he employs a very delicate thermo- 

 multiplier in connection with his six-foot reflecting telescope. 

 Observations made during the eclij^se of the moon showed 

 that the least heat was received from the moon in the middle 

 of the eclipse, when also the least quantity of light was re- 

 ceived, at which time the quantity of heat was only one half 

 of that observed durina: the full moon. From a lonsr series 

 of observations, corrected for the change in the distance of 

 the moon. Lord Rosse is able to draw a curved line, whose or- 

 dinates express the heat, and whose abscissas exj^ress the cor- 



