A paleomagnetic study was made on 747 specimens from 57 sites from Late Cretaceous alkaline rocks in the Nemuro Peninsula, Hokkaido, N.E. Japan (43.3N, 145.8E). Direction of magnetization of samples from the marginal parts of some monzonite or piclitic dolerite complex are quite different from those from the central parts. This suggests that the transitional change of geomagnetic field polarity might have occurred during cooling of the rock body. The paleomagnetic results suggest the presence of two short reversed zones in the Upper Cretaceous in which normal polarity was predominant. Recent K-A age determinations suggest that these reversals took place at 88 m.y. and 84 m.y. ago. They should become important time markers in Cretaceous paleomagnetic stratigraphy.

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Experimental study with Centri-Cleaner to separate vessel elements from wood fibers was carried out using several bleached kraft pulps produced from some tropical and other hardwoods. Vessel separation efficiencies of pulp were examined in detail. It became clear firstly that vessel elements having larger projected area and lower L/D ratio (ratio of longer side length(L) to shorter one(D) of projected vessel element) were separated more effectively into reject side of hydrocyclone. Secondly, separation efficiency varied with pulp species. It was considered that one of the main reasons was the differences of shape(L/D) and size(projected area) of vessel elements. The pulp containing many slender(high L/D ratio) vessel elements had low separation efficiency. Furthermore, the separation efficiency decreased with an increase in pulp consistency for Centri-Cleaner treatment. This is probably due to the development of fiber network in a Centri-Cleaner at high pulp consistency, which would hinder the settling of vessel elements.