TRANS. ST. LOUIS ACAD. SCIENCE. 498 
means of which are printed in full-face type, to distinguish them. 
It will be seen, however, that the means of these periods do not 
progress, rise and fall, much more evenly than the single daily 
means; compare, e.g., the mean of Jan. 31st to Feb. 4th, which 
is so much lower than the mean of the foregoing or the following 
five days that one might suspect a regular and normal decline of 
temperature in these days, and not a mere accident. 
A few facts must strike every one who examines the ta¬ 
bles. The first is, that a time even as long as 47 years fails to 
give us anything approaching absolute and reliable means; and 
we come to the painful conclusion, that observations even contin¬ 
ued for double that time, or for a century, may not yet obtain that 
desirable object. It seems that the excessive extremes of one or of 
a few days such as we often observe in our climate of extremes, 
especially in the winter season, will influence—or, I may say, 
vitiate—the means of a long series of observations ; and the ques¬ 
tion with me arises, whether such extremes ought not to be elim¬ 
inated from the series, and thus truer means be obtained. At the 
same time we may justly be astonished that from such heteroge¬ 
neous data so much order and system result—which gives us 
hope that we cannot be quite on the wrong track. 
Another fact, which strikes us in looking over the tables, is 
that the mean temperatures do not increase and decrease evenly, 
but sometimes quite rapidly, and at other times they may become 
almost stationary for a time. These points come out most strik¬ 
ingly on a diagram which embodies the essential parts of the 
results and shows the daily progress of the temperature. Thus 
we find very little change from the middle of December to the 
first part of February, though the temperature proves to be low¬ 
est from January 4th to 13th ; then we notice a rapid rise from 
Feb. 6th to 20th, a slower rise to the middle of March, then a 
rapid one to the end of the month ; in the forepart of April a slow 
and after the middle of that month a very marked one ; then fol¬ 
lows a tolerably even, at last quite slow, rise to July 9th, when 
between this date and the 18th the greatest elevation of the curve 
is obtained. After that the mean temperature falls slowly to the 
middle of August, followed by a more rapid decline to the end 
of September; after a slight pause in the first week in October, 
a more rapid fall takes place for the following two weeks and a 
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