486 Queries and Answers. 
will be less and less bent when they enter his eye: consequently, the ima- 
ginary water will recede to a greater and greater distance, diminishing also 
in extent. As he sinks down, the reverse will take place : fewer and fewer, 
and at last no direct rays from the hill will reach him, while the refracted 
rays from the sky will arrive more and more bent: thus bringing the watery 
appearance nearer and nearer ; till, finally, when his head is close to the 
ground, every terrestrial object, except the spot on which he is placed, will 
disappear, and he will find himself totally enveloped in what will seem 
tremulous white vapour. — A Subscriber. March 23.1830. 
The Weather; in answer to Mr. Gorrie, — Sir, Your valuable correspond- 
ent Mr. Gorrie (Vol. II. p. 177.) has proposed a few very natural and curious 
questions, which, if satisfactorily answered, may afford some amusement to 
your readers. His questions, in their order, are, first : — 
“ Why is the awn of the wild oat, &c., more straight when the hygrometer 
indicates saturation than when the air contains less moisture ?% To answer 
this, a short description of the awn of the oat must first be given. It 
is composed of two parts, a spirally formed base and a simple bristle-like 
apex : the former is contracted by a rotatory motion in damp, and relaxed by 
a contrary motion in dry, air. The like effects are observable on all cordage, 
string, and every description of twisted material. The water received among the 
plications of the tissue swells the threads of which it is composed: of course, 
each thread is forced from its longitudinal to a more transverse position, 
thereby increasing the diameter of the cord, while it reduces its length. It is 
on account of this property that whipcord, catgut, string, &c., have been used 
to form common hygrometers; and some of the most delicate instruments for 
indicating the state of the air, as to moisture, are formed of the spiral base of 
the wild oat. To be convinced of this moving power of the awn, let the natu- 
ralist separate one from the ear, and, holding the base between his finger and 
thumb, moisten the awn with his lips: it will be seen to turn round for some 
time; which motion is caused by the collapsing of the volutes of the spiral 
base. That the awns are all more straight, and mostly pointed in one direction 
in damp weather, is perfectly true: they are so, because they are coiled up as 
in fig. 123. a; whereas, when the air is dry, they are relaxed into the form 6. 
The use of the ariste, or awns, in vegetable econo- 
lw pee my, is supposed to be for the purpose of attracting 
4 or discharging electric currents necessary for either 
VA the protection or maturation of the plant. 
; Mr. Gorrie’s second question relates to the 
VA collapsing of the flowers and leaves of plants 
4 before rain. Many plants, and particularly those 
Cc! named in the question, take a kind of repose 
rat during the night. The light and heat of the sun 
= are the stimulants to their rigid expansion and de- 
*) velopement: but when his influence is withdrawn 
during night, or partially during the day, the petals 
of flowers contract, and the petioles of leaves lose their rigidity, or relax in 
a contrary direction to what they had in the day; and as rain is commonly 
preceded by a lower temperature and clouded sky, the plants affected by the 
direct influence of the sun are soon sensible of the deprivation, and droop or 
collapse accordingly. Light is, therefore, the principal cause of expansion, 
and the want of it occasions flaccidity. Even artificial light will open flowers 
that have shut themselves up for the night: a crocus has been expanded 
by the light of candles! On this subject it is necessary to add a few re- 
marks, viz.: — Some flowers and leaves seem to be affected by the light, 
and others chiefly by the heat, of the sun; if, however, they receive either 
too intensely, they suffer and are withered. Instead of a temporary cessa- 
tion of their vigour, as is the case before rain, it is an injury which only a 
refreshing shower and darkness can recover. Again, many plants are most 
