532 Proceedings of the Royal Society of Edinburgh. [Sess. 
than by their power of falling through the air. After the 25th the number 
of particles became low, under the influence of a S.W. wind ; and though 
the wind returned to the W. and N.W. on the succeeding days, the high 
numbers did not return, the meteorological conditions having changed, the 
centre of the anticyclone having moved away to S.W., and a general cir- 
culation from the N.W., under the influence of a cyclone to the east, had 
become well established, and all the dust observations were similar to those 
obtained at Kingairloch under the same conditions. 
It may be as well here to give a word of caution as to the comparison 
which we can draw between the figures obtained at Kingairloch and at 
Morar in N.W. winds. It has already been shown that there are certain 
very abnormal numbers obtained at Kingairloch when the wind was from 
the N.W., the numbers going up to 9000 per c.c., and even to 12,000 per c.c. ; 
and there was this peculiarity in those Kingairloch numbers, that they were 
only obtained in sunshine. With N.W. winds the numbers were uniformly 
low on clouded days, and were low on the mornings of sunny days, but 
they gradually rose under the influence of the sunshine, falling low again 
at night. Further, there was another peculiarity in these Kingairloch obser- 
vations — there was no haze corresponding to the high number of particles ; 
the air retained the usual clearness of the N.W. winds. Now the high 
numbers observed in N.W. winds at Morar were also observed in sunshine, 
but, unlike the Kingairloch air, it was densely hazed. The islands of Rum 
and Eigg, distant respectively 16 and 12 miles, were quite invisible, and the 
hills two or three miles away were thickly hazed. The abnormal high 
readings obtained at Kingairloch in N.W. winds still remain a mystery, 
and they have no relation and throw no light whatever on the high 
numbers obtained at Morar in air from the same direction. From this 
point of view, the high numbers at Morar seem to point to the tail of the 
comet as a possible cause, but, from the complication of the evidence, per- 
haps “ Not proven ” is the only verdict that can be safely given. 
Observations on Atmospheric Electricity. 
For the purpose of studying the electrical condition of the atmosphere, I 
was only provided with apparatus of the simplest construction, as all I 
intended was to take eye observations of the sign and the potential of the 
electrification. The apparatus consisted of a common leaf electroscope and 
one of Glew’s Radium Collectors. The collector was hung from the end of 
a fishing-rod which projected from a second-story window looking S.S.E., 
the collector being connected with the electroscope by means of a fine wire 
