G. F. Becker — Fishers Sew Hypothesis. 137 



The latter statement suggested the question, whether the 

 colors so observed, might not be merely the result of tension 

 which must here undoubtedly exist in consequence of the 

 pressure. 



All samples on hand were examined with reference to this 

 property. Thin sections were made with a razor, and. placed 

 without a coverglass on the stage of a polarizing microscope ; 

 every one of them displayed colors more or less striking. 



Then arose the next question: the tension of pressure had 

 indeed been obviated in the last series of tests, but might not 

 the mechanical operation of cutting produce a tension on the 

 surface of the adhesive rubber ? 



To answer this, several tests seemed applicable. By wash- 

 ing a section in chloroform, the superficial layer that might 

 have been stretched in cutting could be removed. By cutting 

 a section with a hot platinum wire, tension was not likely to 

 be produced. By dissolving and then drying rubber it could 

 be examined before any outside force, other than surface ten- 

 sion, could have influenced it. By examining fresh latex, 

 liquid or dried, the properties of the original globules could 

 be ascertained. The results of these different tests agree com- 

 pletely ; no colors appear. When, however, the resolidified 

 rubber or dried latex was sectioned however carefully or 

 quickly, or stretched, colors invariably appeared. These 

 results, and absence of polarization-colors whenever tension 

 was removed, presence of colors where tension might exist, 

 allow but one conclusion. The property of displaying various 

 prismatic colors under the rotating Nicol of the polarizing 

 microscope, probably does not belong as such to any of the 

 varieties of crude rubber brought into our markets, and these 

 colors so frequently noted are best explained as incidental 

 results of the way in which the objects are generally prepared 

 for examination. 



Art. XX. — Fishers New Hypothesis ; by Geo. F. Becker. 



In the June number of this Journal* Mr. O. Fisher reaches 

 the conclusion that on an earth of small viscosity, that is a 

 fluid globe, the height of the oceanic tides would be dimin- 

 ished by only a moderate fraction of its height on a rigid 

 earth. He infers that the existence of tides of short period 

 does not indicate a high value for the rigidity of the earth ; a 

 conclusion of great interest to geologists, some of whom per- 



* Vol. xlv. p. 464. 1 893. 



