7. N. Inoue, D. Kuroiiva, and Y. Takeuchi : Trial Manufacture of 



Electric Visibility Meter— (I ) Summer Fog 



The trial manufacture of an apparatus was made, which is able to 

 measure fog density through night and day by means of light source 

 modulated adequately to photocell receiver. By using the apparatus 

 the relation between fog density and visibility in summer fog and the fine 

 fluctuation of density were studied. 



8. N. Inoue, H. Nakayama, and D. Kuroiwa : Trial Manufacture of 



Electric Visibility Meter — (II) Winter Fog 



By improving the electric visibility meter described previously in 

 item 7 visibility in winter fog and snowfall and the relation between the 

 discernible distance of light source and fog density were studied. 



9. A^. Nakayama : On Method of Use of Wigand's Visibility Meter 



As the results of actual observation using Wigand's visibility meter 

 it was clarified -that error of 20-30 per cent, was caused by instrumental 

 correction and personal error. However, a method was devised which 

 reduces the error by means of measuring two slightly different distances 

 and putting simultaneously three ground glasses with different density 

 into the same visual field. 



Part II — Studies of Physical Properties of Fog 



10. H. Oguchi : Measuremeni of the Radius of Fog Particles at Nemuro 



and at the Top of Mount Niseko 



According to the method of measurement mentioned in the item 1 

 above, diameters were measured for about 150,000 fog particles. These 

 measurements were made in the surface level as well as in a balloon, 

 to investigate the variation of diameter with height. The results thus 

 obtained are as follows : (1) in the case of sea fogs at Nemuro the 

 maximum frequency of diameter distribution was found in the range of 

 10 to 20/z, where the size of each particle was not uniform in general but 

 mixed with more larger particles and fine rain-drops towards the lower 

 level; (2) in the levels near the surface, fogs of dissipation type were 

 frequent, with particles of smaller diameter ; (3) cloud-particles at the 

 top of the Mount Niseko were rather small and uniform in diameter ; 

 (4) it was found that the relation between visibility and diameter of 

 fog-particle can be suitably represented by the Trabert's formula. 



11. /. Sugaya : On the Relation Between the Nature of Fog and the 



Diameter E^strihdion of Fog-particles 



As the results of observations the author identified two kinds of 

 fogs — viz., dry and wet — the difference of which is to be attributed 

 mainly to the rate of capture of fog-particles. In other words, the 

 dryness of a fog becomes greater with increase of the wind speed and 

 decrease of the size of fog-particle. On the basis of this opinion, the 

 critical condition between dry and wet fog was studied. 



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