260 TRANSACTIONS OF THE [mAY 17, 



and of Hall at Washington, deserves especial mention. A new 

 heliometer of seven inches aperture has been ordered for the 

 Cape observatory, and wlien it is received, a vigorous attack is 

 planned by co-operation between tliab observatory and that of 

 Yale College, which possesses the only helionieter in America. 



During the ten years, our knowledge of double stars has been 

 greatly extended; several observers, and most eminent among 

 tliem Burnham, of Chicago, have spent much time as hunters 

 of these objects, and have bagged between one and two thousand 

 of them. Several others, es|)ecially Doberck in England, and 

 Flammarion in France, have devoted attention to the calculation 

 of the orbits of the binaries, so that we have now probably about 

 seventy-five fairly well defined. 



In the study of the nebuhe, less has been done. Stephan at 

 Marseilles and Swift at Rochester have discovered many new 

 ones, mostly faint, and Dreycr, of Dublin, lias published a sup- 

 plementary catalogue, wliich brings Sir J. Herscliel's invaluable 

 catalogue ])retty well down to date. Tiie studies of Ilolden upon 

 the great Orion nebula and the so-called '' trifid nebula" deserve 

 special mention, as securely establishing the fact that these 

 objects are by no means changeless, even for so short a time as 

 twenty or thirty years; also tlie discovery of a new nebula in the 

 Pleiades by means of photography. 



Observatories. 



During the ten years, a considerable number of new observa- 

 tories have been founded. Abroad we mention as most import- 

 ant the observatories for astronomical physics at Potsdam, in 

 Prussia, and at Meudon, in France, also the Bischoffsheim obser- 

 vatory at Nice and its succursal in Algiers. The great observa- 

 tory at Strassburg can hardly be said to have been founded 

 within the period indicated, but the new buildings and new in- 

 struments and new efficiency date since 1880. We ought not to 

 pass unnoticed the smaller observatory at Natal, in South Africa, 

 and the private establishments of von Konkoly at 0-Gyalla, of 

 Gothard at Hereny (both in Hungary), and of the unpronounce- 

 able gentleman Jedrzejewicz at Plonsk, in Poland, and the ob- 

 servatory at Mount iEtna, from which, however, we have no 

 results as yet. 



In the United States we have the public observatories at Madi- 

 son, Wis., at Rochester, N. Y., and at the University of Vir- 

 ginia, and the, as yet, unfinished Lick Observatory in California: 

 also a host of minor observatories connected with institutions of 

 learning, and mainly designed for purposes of instruction; such 

 establishments have been founded within ten years at Princeton, 

 at Northfield, Minn., at South Hadley, Ms., at Beloit, at Mari- 



