1881. ] Geography and Travels. 673 
inches in November to 28.70 in June. The diurnal variation is 
rarely more than twenty hundredths of an inch. The barometer 
is therefore of little use as a weather glass, but, on the other hand, 
is more serviceable for geographical work in the measurement of 
mountain heights. 
“The temperature on Lake Nyassa is very equable. The aver- 
age midday temperature of the hottest month, November, is 85° 
F., and the average night temperature of the coldest month, May, 
is about 60°—a range of only 25° throughout the year. Occa- 
sionally, however, we have days at 95°, and even 100° has been 
registered once or twice. At the other end of the scale, 54° has 
been the lowest. As a general rule the wet-bulb thermometer 
stands at 10° below the dry-bulb throughout the dry months of 
the year.” 
As regards the alteration in level of the waters of Lake Nyassa, 
the observations made at Livingstonia show that “since 1875 the 
low-water level of the lake has year by year been falling, till in 
December, 1880, it was three feet below that of December, 1875. 
Should this decrease continue, the matter will soon become 
serious during the dry season with regard to the navigation of the 
southern end of the lake at the entrance to the Shiré, and still 
level. This clearly accounts for the intermittent character of the 
drainage. There had been a period of very dry seasons, probably 
before this century, in which the level of the lake was lowered so. 
that no water went out by the Lukuga. Gradually a change took 
place; the rainfall became more abundant and the water gradually 
rose until the barrier was swept away and an outlet once more 
formed for the surplus water of the lake as they now had it. 
r. Thomson’s narrative of his journey has been published 
under the title “To the Central African Lakes and back,” and 
contains much of scientific interest. He has a note on the recent 
great improvement in the climate of Zanzibar, the malaria and 
‘ Livingstonia Mission Report for 1880. 
