June 19, 1913] 



NA'l URL 



401 



The interdependence between the amounts of 

 carbon dioxide and oxygen is so constant that 

 carbon dioxide estimations made in the Sonden 

 apparatus may be taken as an accurate indication 

 of oxygen content. For every o'oi per cent, in- 

 crease in atmospheric carbon dioxide, a corres- 

 ponding decrease in the percentage amount of 

 oxygen may be safely assumed. T. E. T. 



THE POTSDAM METEOROLOGICAL AND 



MAGNETIC OBSERVATORIES. 1 

 THE volume referred to below gives a lucid 

 -*■ description of the observatories at Potsdam, 

 compiled by Profs. Suring and Schmidt, who are 

 in charge respectively of the meteorological and 

 magnetic departments. A preface by Prof. Hell- 

 mann, the director of the Royal Prussian Meteoro- 

 l'>'i',il Institute, to which the observatories be- 



obsen atories — also situated on the Telegraphen- 

 berg — admits of the ready exchange of ideas 

 amongst a number of men of science, each an 

 expert in his own subject. The figure reproduced 

 shows the enclosure devoted to meteorological 

 instruments, especially those recording air and 

 earth temperatures and rainfall. The small build- 

 ing in the corner is devoted to atmospheric elec- 

 tricity. In the background is the main meteoro- 

 logical building, a very large and handsome struc- 

 ture. Its basement contains inter alia a physical 

 and chemical laboratory, a photographic dark- 

 room, a workshop, electrical generating apparatus 

 and storage batteries. 



On the ground-floor are various rooms for 

 meteorological work, including a large room con- 

 taining" the barographs and other recording instru- 

 ments. Most of the remaining space under the 

 roof serves to provide accommodation for the 



long, states that the book is primarily intended 

 for the benefit of those studying at or visiting the 

 observatories, the number of visitors being now 

 large. The text describes the buildings and instru- 

 ments, while reference is made in footnotes to 

 many researches associated with the place. Thirty- 

 one figures supplement the descriptions of build- 

 ing's and instruments in the text, and a plate gives 

 a ground-plan of the whole site. 



The construction of the magnetic observatory 

 began in 1888, and that of the meteorological 

 observatory in 1S90, so that the buildings are 

 all modern. The equipment is also modern and 

 exceedingly complete. The site on the Tele- 

 graphenberg, a wooded hill on the outskirts of 

 Potsdam, might be criticised by some meteoro- 

 logists, but it possesses much natural beauty, and 

 the proximity of the astrophysical and geodetic 



227;, VOL. 91] 



! 3 marks 



r P . e 7 + 



il and magnetic observatories at Potsdam. 



resident staff and the director of the Meteoro- 

 logical Institute, but it includes a library and a 

 conference chamber. The roof is flat and sur- 

 mounted by a low and a high tower, the former 

 devoted to optical and cloud-measuring apparatus. 

 The large tower rises to a height of 32 metres 

 above ground-level. A staging on the top of it 

 carries various wind-measuring apparatus, in- 

 cluding a Robinson anemometer, the cups of which 

 are 40*8 metres above the ground and surmount 

 all other objects on the Telegraphenberg. 



There are two chief magnetic buildings, the 

 larger about 100, the smaller about 150 metres 

 from the meteorological building. The former 

 contains two sets of magnetographs, in a basement 

 maintained at a nearly constant temperature 

 throughout the year ; the latter is devoted to 

 absolute observations. In view of electric-tram 

 disturbances in Potsdam — though these are still 

 exceedingly small — a new magnetic observatory 



