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POPULAR SCIENCE MONTHLY. 



Vincey, of the French School of Agriculture, 

 as hygienicallj" and economically the most 

 perfect. The work is done through the nitric 

 oxidation of nitrous organisms effected, in- 

 dependent of vegetation, by special microbes 

 contained in the soil. The nitrates thus 

 formed, combined with the very soluble 

 bases contained in the earth, are taken up as 

 foods by plants or carried off in drainage 

 waters. The purifying quality of the soil is 

 not augmented by the production of crops 

 upon it. The siliceous sewer beds of Genne- 

 villiers, near Paris, dug up and ridged, with- 

 out crops, are capable of absorbing and puri- 

 fying 1,200,000 cubic metres of sewage per 

 hectare (about two acres and a half) a year. 

 Agriculture is regarded as of great impor- 

 tance in the economy of sewer beds, but not 

 so much on account of its relations to purifi- 

 cation as to the quantity of water which the 

 ground can receive. The demands which the 

 most thirsty crops can make upon the water 

 constituents of sewage are, however, limited ; 

 and they absorb only a fraction of the amount 

 poured upon the beds. M. Vincey's observa- 

 tions in the Agricultural Park of Asnieres in- 

 dicate that forest land is capable of usefully 

 purifying at least as much water as the 

 natural meadow ; and it results from all the 

 experiments that, for a like soil and equal 

 volumes of sewage, a smaller surface of 

 meadow or forest is required than, for in- 

 stance, of kitchen-garden crops. Siliceous 

 soils and sands free from marl appear to have 

 the highest purifying qualities. Limestone 

 formations, marls, clays, etc., are inferior in 

 these properties. The longer a soil has been 

 purifying sewer water, the fitter it becomes 

 for continuing the work ; for purifying irri- 

 gation multiplies the colonies of mineralizing 

 ferments in the soil. Comparative examina- 

 tion of land in which the operation had been 

 going on from ten to twenty years and of 

 soil that was virgin to the process, showed 

 that no nitrogen had accumulated in the 

 earth in consequence of sewage irrigation. 

 The smaller part of the mineralized matter 

 passes into the crops, while the larger part 

 is washed away. 



Cycles and Dogs in War. The utility of 

 bicycles in military art having been demon- 

 strated, men of war are now studying the 

 means of contending against them and their 



riders. The mere overthrow of the instru- 

 ment does not convey any great advantage, 

 for the man is there, and possibly still stand- 

 ing, armed, and ready to fight. Dogs have 

 so far seemed to be the most effective agents 

 in this contention, and the large Danish dog 

 has been selected as the animal most fit. 

 About a thousand dogs are said to be under 

 training in Berlin for this sort of warfare. 

 They are taught to distinguish the uniforms 

 of friends German, Austrian, and Italian 

 from those of the enemy French and Rus- 

 sian and attack the latter, the legs of the 

 sham " hostile " soldiers being well pro- 

 tected, of course, by stout buskins. As all 

 the armies will have cycle troops, they will 

 all have to have their trained war dogs; 

 and then, when the attack has commenced, 

 La Nature slyly intimates, and the dogs get 

 mixed with the cyclists, they will leave the 

 soldiers and go to fighting one another. 



Hydraulic Blasting. A meeting of the 

 Manchester Geological Society is reported in 

 Industries and Iron, at which a new hy- 

 draulic apparatus for breaking down coal 

 in mines was discussed. Mr. James Tonge, 

 who described the apparatus, called atten- 

 tion to the great danger attending the ordi- 

 nary method of blasting in coal mines, and 

 said that the numerous serious accidents 

 from this cause had led the inventors to look 

 for a safer process of loosening the coal. 

 The new apparatus consists of a hydraulic 

 cartridge, eighteen inches in length and three 

 in diameter, and weighing thirty pounds, 

 and a small but powerful hand pump fitted 

 with a pressure gauge weighing about 

 twenty pounds. The mode of using it is as 

 follows : The coal is holed underneath the 

 usual depth, and a hole drilled near the roof 

 to about the same depth as the holing, in the 

 same w^ay as for blasting. After this the 

 cartridge is placed in the hole and pushed 

 to the back. No " stemming " is required. 

 The pump is coupled to the cartridge, the 

 suction pipe placed in a small bottle of wa- 

 ter, and work commences. Very soon the 

 gauge begins to show the rising pressure 

 half a ton, a ton, a ton and a half, two tons 

 to the square inch. During this time a 

 cracking sound is heard, indicating the shear- 

 ing off of the coal at the back. The gradual 

 way in which the work is done, without shock 



