ASTRONOMY. 13 



The chief signal-officer of the army has proposed to the 

 various observatories of this country, both public and pri- 

 vate, to co-operate in physical observations of the sun. Ev- 

 ery phenomenon of interest should be registered, whether re- 

 lating to spots, faculae, or protuberances, etc. Each observ- 

 atory that is willing to take up any special field, or that al- 

 ready occupies such a field, is requested to give its results, 

 or such part of them as it is willing to give, to the Signal 

 Bureau for record in its Monthly Weather Eeview. Thus a 

 prompt publication is secured. In response to this invita- 

 tion, a record of the number of spots daily observed on the 

 sun's disk is prepared by Mr. D. P. Todd, of Washington. It 

 is to be hoped that a regular series of photographic records 

 of sun-spots can be made by some one or more observato- 

 ries in the East, and by at least one on the western coast. 

 In order to render such observations of the sun complete, 

 the establishment of these stations and one in Japan is 

 required. 



Sun-spots continue to be observed photographically at 

 Greenwich, Paris, Moscow, Toulouse, Kasan, Vassar College, 

 and are observed visually at Madrid, Oxford, Berlin, Zurich, 

 Leipsic, and Potsdam. 



Protuberances are observed at Palermo, Rome, Greenwich, 

 Moscow, O'Gyalla, Potsdam, etc. 



Professor Langley, of Allegheny Observatory, and Dr. 

 Huo-rrins, of London, some years as;o described the granular 

 surface of the sun's photosphere. Their division of the 

 brighter aggregations of the surface was (successively as to 

 size), first, cloud-like forms, perceptible to telescopes of ordi- 

 nary power ; second, " rice-grains," or nodules, of which such 

 forms are composed, the rice-grains being perceptible with 

 higher powers and good definition ; third, granules compos- 

 ing the rice-grains. The discovery of the granules has been 

 independently made by the photographic researches of M. 

 Janssen, who has succeeded in obtaining photographs of the 

 sun with only a( / uo of a second exposure. These were pro- 

 cured with lenses of long focus, and a slow development of 

 the image. The "willow-leaves" or "rice-grains" of pre- 

 vious observers appear in these photographs only as occa- 

 sional ao-oTeo-ations. The main feature is an abundant gran- 

 ulation. The forms of the oranules are sufficientlv defined 



