130 
MAGAZINE OF SCIENCE AND ART, 
There can be no doubt but that the relation between 
the evaporation and either of the before mentioned 
differences, must, in reality, be complicated by terms 
involving the atmospheric pressure and temperature ; 
if however we adopt the first assumption, 1 am con¬ 
vinced that the errors thus introduced will be small, 
and will quite disappear in the calculation of moan 
results for months and years. 
The great, difficulty which presents itself is, that the 
surfaces of rivers, Jakes, &c., are generally exposed to 
the sun and wind, whilst the instruments are protected 
from both; something however may bo done towards 
removing this difficulty, by experiments for determining 
the effect of the sun and wind on the indications of the 
hygrometer. 
The best method of conducting the -experiments on 
evaporation is still under consideration, and I shall be 
obliged to any member of the society whose experience 
may enable him to assist me with suggestions on the 
subject. 
According to the views which I have stated it will be 
unnecessary to experiment on evaporation at any of the 
branch observatories, for if the supposed relation can 
once be satisfactorily established at one place, the 
evaporation at any other place where the readings of 
tlie dry and wet bulb thermometers are registered can 
be obtained by a simple arithmetical process. 
I have been induced to enlarge somewhat on this 
question, partly because it seems to excite considerable 
interest in the colony, and partly because there exist, 
even amongst well informed persons, some misconcep¬ 
tions on the-subject. Thus, in a scientific publication. 
I noticed, not long since, that one writer had assumed 
the evaporation in Australia to he the same as in 
England, and another that the evaporation was propor¬ 
tionate to the mean temperature; whereas it will un¬ 
doubtedly bo found that the ratio between the evapora¬ 
tion at many of our ini and stations and that of England, 
will, on account of the dryness of the air, greatly ex¬ 
ceed the ratio between the mean temperatures. 
Amongst the instruments sent out From England are 
twelve DanielTs hygrometers: these I fear will be of 
very little service to us, for when the air has been very 
dry, I have found it sometimes impossible, partly 
owing, perhaps, to the inferior quality of the tether, to 
obtain the deposit of dew on the bulb : even when the 
desired result can he obtained, the readings are in such 
cases probably incorrect, in consequence of the proxi¬ 
mity of the observer to the instrument for so great a 
length of time. 
The remaining instruments are a rain gauge, a wind 
vane, and an electroscope; the latter is a common gold 
leaf electroscope for determining the quality, but not 
the intensity, of any considerable electrical disturbance 
in the atmosphere : the electroscopes will be used only 
at such of tlie stations as mav seem most convenient 
and suitable for the purpose. The shade thermometers 
are mounted on a stand resembling that used at Green¬ 
wich, <vith some little addition of my own to remove 
the necessity of a frequent change of position. 
The instruments will be read three times a day, 
namely, at 9 a.m., 3 and 9 p.m.; the registers will be 
s ent monthly to the Sydney observatory, where all com¬ 
putations and reductions will be made. 
Having now given a brief statement of what is in¬ 
tended to be done for the science of meteorology in this 
colony, I may conclude with the hope, that when next 
I call your attention to the subject, it will be to lay 
before you some results of our labours winch may, 
perhaps, furnish materials for a paper of a more inter¬ 
esting character. 
It may be as well to state here, that Messrs. Flavelle 
are prepared to furnish amateur observers with sets of 
instruments exactly similar to those used in the govern¬ 
ment observatories at a very moderate price. 
ON THE STRUCTURE AND FUNCTIONS 
OF THE VENOM APPARATUS IN 
SERPENTS. 
By Alfred Roberts, Esq. 
The structure of the poison fang, in relation to its 
groove or canal, has been deeply investigated in 
common with tlie general organism of serpents, 
but there are other points scarcely less interesting 
or important, which have not, as far as I can ascer¬ 
tain, been sufficiently elucidated—and some of 
these, this colony affords facilities for studying. 
With this feeling, and under the impression that 
the most trilling contributions to the minute ana¬ 
tomy of any portion of the animal kingdom, is 
acceptable to the physiological Zoologist: finding 
also, as the subject opened to me, that the serpents 
of this country had scarcely received the attention 
which their importance demands, I resolved, when 
the opportunity offered, to examine the general 
character, appendages, and structure, in the prin¬ 
cipal varieties of the terrestrial and pelagic serpents 
of Australia. 
I should have been glad to complete the series of 
dissections which I have in view, and defer any 
notice of them, until 1 was enabled to lay before 
you an abstract of tlie whole, with such observations 
as might then appear necessary. 
This is, however, at present impossible, and I 
must content myself with bringing before you, from 
time to time, the results of a dissection and micro¬ 
scopical examination of such specimens as I am 
enabled to investigate. 
It will be first necessary to notice tlie present 
systems of classifying snakes, and to consider, whe¬ 
ther it is of a character likely to afford a ready as 
well as just acquaintance of the subject. If this 
should prove not to be the case, I shall venture to 
offer such suggestions for its modification, as may 
be deemed likely to render it more generally useful. 
The present mode of classification is well exem¬ 
plified in the following table, for which I am 
indebted to the kindness of Mr. Win. Macleay, who 
abridged it for me from Ihe valuable work of Du- 
meril and Bibron. In his opinion it is far the best, 
as it is the most simple, that has been hitherto pub¬ 
lished. 
In this system, as in others, the order Ophidia is 
divided into two families—Innocua and Venenosa; 
which are again divided into five genera, the latter 
having their species, &c. 
It will be seen hereafter, that the genus Soleno- 
glypha does not exist; but I wish now, more espe¬ 
cially, to draw your attention to the manner in 
which the division into families is effected. 
In characterising these by the terms Innocua 
and Venenosa, a distinctive name is given to each, 
which should convey a correct idea of their respec¬ 
tive qualities; or, in other words, it is implied by 
such a nomenclature, that while one variety is 
harmless and innocent, the other is dangerous and 
venomous; blit no inference is offered of what I 
believe to be the primary function of the so-called 
poison apparatus. 
With the exception of the Opoterodonta, all 
snakes attack living food, and all have the means of 
rendering it powerless before taking it into the 
system. The Boa tribe perform this by constric¬ 
tion ; the prej T is encircled and compressed by the 
reptile, and when powerless, or dead, is slimed over, 
after which it is slowly taken into the mouth, from 
whence it gradually passes into the digestive tube.. 
