-MASSKS OF VISUAL I'.INARV STARS. 4~_^ 



of the 15th magnitude, would liave a total mass ec|ual to that of 

 the Sun's, and yet its combined light would result in the mag- 

 nitude 7.5 or 2.5 magnitudes brighter than the Sun at the same 

 distance. In all but the very largest telescoi)es, such a cluster 

 would be irresolvable into stars. 



Si'MMARv. — Few double stars have gravitative power so 

 great as that of the Sun. (iravitative power is small in stars of 

 spectral classes B and A, n.ioderate in F". and large in G and K. 

 It seems to be absent in classes Oe and M. Inhere appears to be 

 a limiting distance below which double stars cannot exist, and 

 for solar-type stars this appears to l)e about five times the Earth's 

 distance from the Sun. \''ery faint binary stars are only found 

 in {)roximity to bright stars. It is suggested that light-pressure 

 may partly or whollv neutralise gravitative ])ower in stars of 

 great luminosity and small tenuity. 



Carbon Bisulphide and Plant Grow^th. — In 



191 1 E. B. Fred, Agricultural Bacteriologist, in the Agricultural 

 Experiment Station of the University of Wisconsin, ])ublished 

 data to show the l^eneficial eltect of carbon bisulphide on the 

 soil flora.* The increased plant grow^th following on tlie addi- 

 tion of carbon bisulphide is in many cases enormous, a small 

 application often cavising an increase in yield from 100 to 200 

 per cent. But in some cases carbon bisulphide not only fails to 

 cause an increase in plant growth, but, on the contrary, has 

 caused a decrease. The author of the former ]ia]ier accordingly 

 studied some of the factors that might influence this peculiar 

 action of carbon bisuli^hide, and has recently jniblished his results 

 in the Joiinial of Aijricitiiural RcscarcJi.i The addition of carbon 

 bisulphide to soil, he states, exerts a decided efifect on the fauna 

 and flora of the soil. This is characterised by a temporary reduc- 

 tion in the number of micro-organisms. Later, an enormous 

 multiplication of bacteria takes place, and an almost parallel 

 increase in production of by-products or soluble nitrogen is 

 noted. The ammonia-content seems to follow^ the curve of 

 bacterial growth, and later gives way to larger amounts of 

 nitrate. From the evidence it seems that carbon bisulphide in 

 soil produces an increase in soluble comjjoiuids of nitrogen and 

 sulphur. It is clear, however, that carbon l)isulphide does not act 

 alike in all soils, or tow^ard all crops. 



* Ceutralblatt fiir Bakferiolofiie 31, 185-245. 



t ( if;i6) 6 [t i 1-20. 



