580 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



TABLE II. 

 Adgust 28. Light Pressure. Ballistic Measurements. Air. 



suring the distance between the centres of tlie images when on the east 



and west vanes (by the dividing engine To, Fig. 3) and dividing by two. 



C + D C + D 



The columns headed — ^-— — ^ = P^ and ^ — - = Pg are the average 



