32 ANNUAL EECORD OF SCIENCE AND INDUSTRY. 



These have long remained in the possession of the family, but 

 the Belgian Academy has now resolved to publish such of 

 these works as have been presented to it, especially a memoir 

 of one thousand pages of descriptive manuscript text, and two 

 hundred and seventeen drawings of the planet Mars, as ob- 

 served between 1785 and 1803. The value of this work to the 

 present generation of astronomers is very highly estimated. 

 Schroeter was unexcelled in the accuracy of his work, and he 

 has here dealt with all those details of his subject that have 

 for some years past been so attentively studied by those who 

 possess good telescopes. His attention was particularly given 

 to the spots on Mars, both those that served to determine its 

 rotation, and also the bright spots at its poles. Schroeter 

 thought that the black spots belong to the clouds of Mars, 

 which have a less reflecting power than the solid portions of 

 the planet. Bull. Acad. Belgique., 1873, 352. 



EECENT OBSERVATIONS ON THE PLANET MAES. 



The last volume of the Annals of the Observatory of Ley- 

 den contains an investigation by Kaiser, the director of that 

 institution (whose recent death we have had occasion to an- 

 nounce), upon the spots of the planet Mars, and the conclu- 

 sions that may be drawn from their study. Besides his own 

 observations. Kaiser had at his disposal some four hundred 

 and twelve drawings published by previous astronomers since 

 the year 1636. Concerning these latter, Kaiser says that he 

 finds such great discordances between them that one can 

 scarcely believe that they refer to the same body ; but while 

 these diflerences are partly due to the fact that only those 

 portions of the planet which are directly opposite to the ob- 

 server can be distinctly seen, he attributes them principally to 

 inexperience on the part of the observers, and want of uniform- 

 ity in their methods of drawing. Perhaps the greatest differ- 

 ence is noticed among the drawings made in 1862 by the most 

 exi^erienced observers furnished with the most jjowerful tele- 

 scopes. Of his own drawings. Kaiser publishes twenty-one en- 

 gravings ; and, from very careful comparison with all the pre- 

 vious ones at his disposal, he concludes that the time of rota- 

 tion of Mars about its axis (which is known to be about once 

 in one day and thirty-seven minutes) can not be determined as 

 accurately as some astronomers have supposed ; and that a 



