EFFECT OF IMPACT UPON BEAMS. 
621 
as noted down by the wardens and of- 
ficers of the watch, during every hour 
of the day and night, commencing on 
the 1st, of May, 1832, and terminating 
in December, 1834, which are also 
checked by a concurrent series of ther- 
mometrical observation, registered eve- 
ry two hours, at the request of the Asso- 
ciation, by the late lamented Mr. Har- 
vey. 
Thus have been afforded us, for two 
complete years, observations to con- 
trast with those taken during 1834 and 
1835, at Lieth Fort, under the superin- 
tendence of the Royal Society of Edin- 
burgh. 
Mr. Snow Harris has deduced from 
an everage of these observations the 
following important results 
1st, The mean temperature of various 
seasons, as well as that of the entire 
year. 
2ndly, The daily progression of tem- 
perature. 
3rdly, The two periods of each day 
at which the mean temperature occurs. 
4thly, The relation between the mean 
temperature of the whole twenty-four 
hours, and that of any single hour. 
6thly, The average daily range for 
each month. 
6thly, The form of the curves des- 
cribed by the march of the temperature 
between given periods of the day and 
night. 
In this manner has been accomplish- 
ed one of the first undertakings suggest- 
ed by the British Association to its num- 
bers, and promoted by its funds, and the 
true form of the diurnal and annual 
curves in an important station of our 
southern coast been attained, as a stan- 
dard of comparsion with that arrived at 
by Sir David Brewster in the latitude of 
Edinburgh, and from which they exhi- 
bit in the results some extremely curi- 
ous and important discrepancies. 
Professor Phillips and Mr. Gray have 
presented us with a continuation of 
those curious observations on the Quan- 
tities of Rain falling at different eleva- 
tions, which had formed the subject of 
two preceding communications publish- 
ed in these Transactions. ' 
In the first series of these, it had been 
shown that the difference between the 
quantities of rain that fell depended on 
two conditions — 1st. the height, and 2nd- 
ly, the temperature; the former circum- 
stance determining the ratio of the dif- 
ference between the two stations, and 
the latter its amount. 
In the second series he showed that 
the ratio likewise varied at diflferent 
seasons. 
The present or third series presents 
us with a formula for expressing these 
variations, and points out its corespon- 
dence with the observations made. 
That the quantity of rain which falls 
should be greater at lower than at high- 
er elevations, is a result which, though 
at first sight it may to appear parado- 
xical, is quickly perceived to harmonize 
with the fact, that drops of rain descend 
from a colder to a warmer atmosphere 
and consequently condence a portion of 
the aqueous vapour which exists sus- 
pended in the lower strata. But that 
the rate of increase should actually be 
found reducible so nearly to a mathe- 
matical formula, is certainly far more 
than could have been expected, and its 
successful accomplishment is calculated 
to give us hopes that other meteorolo- 
gical phenomena, which seem at present 
so capricious as to baffle all calculation, 
may at length be found reducible to 
certain fixed principles. So far as relates 
to the rain that falls at York, the results 
are regarded by Professor Phillips as 
sufficiently complete, but he strongly 
urges the advantage of instituting in 
other spots selected m different parts of 
the kingdom similarobservations, which, 
if executed simultaneously, would 
mutually illustrate each other, and be 
likely to throw much additional light on 
the theory of rain, and on the distribu- 
tion of vapour at different heights 
An important practical paper has 
been published in our Transactions of 
this year by Mr. Eaton Hodgkinson, on 
the effect of impact upon beams. It is a 
continuation of some researches which 
he communicated at the preceding 
Meeting, on the collision of imperfectly 
elastic bodies. In these experiments he 
had laid down the general principles 
relating to the collision of bodies of dif- 
ferent natures, and had obtained, a- 
mongst other results the following, — 
namely, that all rigid bodies possess 
some degree of elasticity, and that a- 
mongst bodies of the same class the 
hardest are generally the most elastic. 
It remained to be seen whether this 
difference in elasticity influenced the 
force of their impact, and this he has 
shown in his present memoir not to be 
