OF ARTS AND SCIENCES: OCTOBER 11, 1870. 299 



Six hundred and twenty-fourth Meeting. 



October 11, 1870. — Monthly Meeting. 



The Corresponding Secretary in the chair. 



The Corresponding Secretary read a letter from the Ameri- 

 can Oriental Society, thanking the Academy for the use of 

 their room. 



Professor Joseph Winlock exhibited a contrivance for record- 

 ing the position of lines in the spectrum, especially adapted to 

 solar eclipses. A silver plate is attached to the telescope of a 

 spectroscope, and a graver to its stand. By a simple motion 

 the position of any line may be permanently recorded and 

 afterwards measured. The principal lines of the solar spec- 

 trum are first recorded, the plate is then moved slightly back- 

 wards, and a number of spectra may be drawn on the same 

 plate and compared with one another. Since the spider-lines 

 may be invisible on account of the darkness, a break is made 

 in the one which is vertical, and a spark from a Ruhmkorff coil 

 passed through it, thus giving a bright spot of light. He pro- 

 posed to apply this method of recording to determine the decli- 

 nation of a star in meridian instruments. 



Mr. George W. Hill presented a paper on the determination 

 of the mass of Jupiter from its effect on the asteroids. Those 

 are selected whose time of revolution is nearly one half that 

 of Jupiter, and the perturbation thus produced is one of the 

 largest in the solar system. 



Professor N. S. Shaler made a communication on the figure 

 of the continents of Mars, compared with those of the earth. 

 In both there is a tendency to point towards one pole, — those 

 of Mars to the north, of the Earth to the south. 



Remarks on this subject were made by Professors Lovering, 

 Whitney, and Winlock. 



Dr. E. H. Clark made a communication on hydrate of chlo- 

 ral, supplementary to one made by him three months or more 

 ago. He stated that physiological experiments on man and the 

 lower animals with this substance had shown it to possess a 



