RORAIMA MOUNTAIN. 
169 
its nasal end, where it forms a trumpet-like dilatable open¬ 
ing on the side of the pharynx just behind and above the soft 
palate (velum) and tonsil. The use of the tube is to preserve 
an equilibrium between the air within and without the 
tympanum, and to sweep away, by means of its cilia, the 
mucus secreted in the cavity of the tympanum and by its own 
walls. The outer air is constantly varying in density, and, 
were the drum a closed chamber, the membrane would be 
liable to strain from without with each increase in density of 
the outer air, and from within with each decrease. The 
sense of pain felt in the ears when going up in a balloon 
or down in a diving bell, and sometimes also after vigorously 
blowing the nose, is relieved by repeated swallowing, which 
act dilates the pharyngeal end of the tube for the admission 
of air from the mouth and nose, thereby equalising the 
density of the tympanic and external air. 
(To be continued.) 
RORAIMA MOUNTAIN.* 
BY W. P. MARSHALL. 
Roraima is a remarkable mountain in South America that 
has just been ascended for the first time by a special traveller 
and botanist, who have obtained some very interesting results. 
The mountain is in British Guiana, near the middle of the 
northern coast of South America, about 200 miles distant 
from the coast and close to the boundaries of Brazil on the 
south, and Venezuela on the west. British Guiana is a state 
about equal in size to England, containing several ranges of 
mountains of moderate heights (about the height of those in 
Great Britain) ; but one mountain, Roraima, the highest of 
them, is 6,000 feet high, or half as high again as Ben Nevis, 
our highest mountain. The country is tropical, being within 
five degrees of the equator, and is a specially rich orchid 
region; the approach to the mountain is difficult, and is 
described as “four days’ walking through a purely savannah 
but most glorious country, and over splendid mountain passes, 
leading to an inconceivably magnificent valley on the southern 
slope of Roraima.” 
* Transactions of the Birmingham Natural History and Micro¬ 
scopical Society. 
