.254 Proceedings of the Boijal Iri^h Academy. 
that it may be expected that a very large number of persons will soon 
make a daily practice of consulting them, and that in this way a 
knowledge of some of the main facts of meteorology in a correct form 
and on a large scale wall become familiar to many minds. And when 
we recollect the small number and the peculiar tastes of the persons 
who have hitherto addicted themselves to meteorological pursuits, I 
think we may reasonably expect, and expect with some confidence, a 
marked increase in our knowledge of the science as a result of such an 
increased area of mind as is now being brought acquainted with the 
subject. 
I think, then, that any suggestion which should have the effect of 
clearing the information daily given in these reports from unnecessary 
complication, and which should bring into prominence their connexion 
wiih the passing phase of the weather, would do us the double service 
of rendering the reports more useful as materials from which forecasts 
can be made, and of inducing a larger number of persons to make a 
practice of consulting them, so as to sow the seed of future meteoro- 
logical discoveries in a greater number of minds. The hope of these 
advantages has induced me to submit the following suggestion to the 
judgment of the Academy. 
The suggestion which I have to offer is a change in reducing the 
observations, which would affect all the meteorological elements, but 
it would produce its most conspicuous effect, and at the same time an 
effect which could be easily dealt with, upon the records of tempera- 
ture. I will therefore speak first of temperature, and afterwards seek 
to show that the same mode of treatment may, with advantage, be 
applied to the pressure, the rainfall, and even to the wind and the 
state of the sky. 
Each of the daily reports is accompanied by four charts, of which 
one is intended to present to the eye the general state of affairs as 
regards temperature at 8 o'clock in the morning throughout the area 
of observation. Eight o'clock in the morning was no doubt selected 
because it is known to meteorologists that the temperature and pressure 
at that hour are very nearly identical with the average of the values 
of these elements throughout the whole twenty-four hours. The 
temperature charts may accordingly be regarded as exhibiting to the 
eye the average temperature for the day of observation. The tempera- 
tures at several of the stations are plotted down upon the map, and 
isothermal lines are drawn in conformity with them. 
Let us then consider what it is that determines the positions of 
these isothermal lines upon any particular day. They in the first place 
depend upon the latitude, since cceteris paribus they would be lines 
parallel to the equator, representing temperatures becoming lower and 
lower in passing from the torrid zone towards the pole. In the next 
place, they undergo an annual change of position depending upon the 
season, travelling towards the pole in summer, towards the equator in 
winter. In the third place, they are affected by the locality, crowding 
together near the seacoast in summer and winter, moving asunder in 
