130 JOURNAL OF FORESTRY 



recommended as a standard hardwood flotation oil. (3) Ketone resi- 

 due in the crude state can also be considered a satisfactory flotation oil 

 for commercial use on cobalt area silver ore and other ores. 



For those who are not familiar with this newest, now widely dis- 

 cussed, process of recovering metals from crushed ore, a few sentences 

 will make it clear : 



The flotation process for the concentration of ores is a method by 

 means of which one or more of the minerals in the ore (usually the 

 valuable ones) are picked up by means of a liquid oily film and floated 

 at the surface of a mass of fluid pulp. Here they are separated from 

 the other minerals, which remain immersed in the body of the pulp. 

 The importance of flotation lies in the fact that it is primarily a "slimes 

 process," by means of which the particles of valuable mineral, too fine 

 for efficient gravity concentration, are saved, with a high percentage of 

 recovery. Recoveries in the mills treating low-grade copper sulphide 

 ores have been advanced 10 to 20 per cent by the installation of the 

 process, and similar increased savings have been accomplished by the 

 same means in mills treating sulphide ores of zinc and lead. 



Monthly Bulletin of the Canadian Mining Institute, October, November, 1917, 

 pp. 856-875 ; 927-949- 



MISCELLANEOUS 



The propagation of spineless prickly pears has 

 Prickly been the subject of experimentation for several 



Pears years by J. H. Maiden, botanist at Sydney, South 



. as Australia. These experiments are now aban- 



Food doned, having proved that the opuntics in their 



quality of drouth resistance are unequaled, but 

 that as a fodder plant its cultivation cannot be recommended in the dis- 

 trict of the experiment. The fruit, as an article of diet, has little or no 

 value, and even the drouth resistance is a negligible virtue, possessed 

 at nearly the same degree by such plants as old man saltbush. The 

 liability to revert to spines was not very marked and not sufficient to be 

 harmful to stock. The fruit, however, has always been very spiny. A 

 table gives detail for twenty varieties cultivated. 



The Agricultural Gazette of Nezv South Wales, October, 1917, pp. 740-742. 



