4 SPONGE SPICULES IN SWAMP SOILS. 



From these results it would seem that the spicules are practically 

 confined to the first 6 inches of surface soil. A few appear at 12 

 inches, although they are absent from the 10-inch sample, but this 

 irregularity may be due to some disturbance of the soil strata or to 

 the fact that the 10-inch sample was taken from a ditch. 



The treatment of soil in which the spicules are present hi quantity 

 must be regarded as a physical problem, as the spicules are siliceous 

 in character and there is no practical method for then* removal by 

 chemical means. The presence of the spicules in the soil up to 4 or 5 

 per cent does not seem to have any bad effect, but with larger quan- 

 tities the disagreeable results ensue. The microscopic spicules are 

 like finely divided glass and cut into the flesh of man or beast, and 

 upon the quantity of the material depends the severity of the result. 



It has been observed that in parts of the affected district where 

 sand has been washed over the land the unpleasant results are not 

 observed, and it appears that the best way to solve the problem is 

 to mix some other soil with the infested soil. The most convenient 

 and practical way to do this is by mixing some of the subsoil with 

 the surface soil, and since in the worst infested areas the presence 

 of the spicules is confined to the first 6 inches, this can be done with 

 comparative ease by deep plowing. 



It is very likely that no bodies of fresh water exist for a very long 

 period without a growth of fresh-water sponge and the consequent 

 deposition of the sponge spicules. Their presence in unusual quanti- 

 ties presents a subject of practical interest. It is suggested, then, 

 that in areas where drainage is contemplated the soil from the lake 

 bed or swamp be examined microscopically for these remains. If 

 present in considerable quantities the depth of the deposit and the 

 possibility of admixing extraneous material to ameliorate the con- 

 dition should be determined. 



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