gil 
Marcu 14, 1884.] 
geographical or topographical reasons for them. 
A comparison of reliable observations, made 
during this period, furnishes evidence of the 
great importance of considering the situation 
and exposure of thermometers. 
In the state of Ohio, there were three dis- 
tinct periods of great depression during the 
month ; and at two of these the minimum tem- 
peratures were unprecedented in the history 
of the state. The important fact, however, to 
which it seems desirable to call attention, is 
that the records of the U.S. signal-service ob- 
servers contain no account of these extraordi- 
nary cold-waves; and we should be ignorant 
of their existence, if obliged to depend for in- 
formation upon these records alone. This fact 
ean be attributed, in some degree, to the small 
number of regular signal-service stations in the 
state, but in a far greater degree, in the opinion 
of the writer, to the situation and exposure of 
the thermometers of that service. 
The Ohio meteorological bureau has more 
than twenty observing-stations, pretty well 
distributed over the state. The observers are 
generally persons of more than ordinary intel- 
ligence, and many of them have had long ex- 
perience in meteorological observations. The 
instruments which they use are of the best pat- 
tern, being similar, in fact, to those in use by 
the U.S. service; and all have been compared 
with the standards at Washington, thrbugh the 
kindness of the chief signal-officer, and their 
elrors are in most cases very small. 
The U.S. signal-service has four regular sta- 
tions in Ohio, situated at Toledo, Cleveland, 
Columbus, and Cincinnati. <A station at San- 
dusky has recently been re-established ; but re- 
ports have not been received from that station, 
for the month of January, by the Ohio bureau. 
The first cold-wave was most severe on the 
Sth, 6th, and 7th. On the 5th the mean mini- 
mum for the state, from the observations of the 
State service, was —16°; and from those of 
the U.S. service it was —12°. The lowest 
temperature recorded by the State service was 
—24.4° ; and by the U.S. service it was —16.38°. 
On the 6th the mean minimum and the lowest 
temperature, as recorded by the State service, 
were —15.3° and — 24.6° respectively, the cor- 
responding numbers from the records of the 
U.S. service being —12.2° and —20.3°. On 
the 7th the difference was still more marked ; 
the numbers being —11.6° and —19.6° for the 
State service, and —2° and —7° for the U.S. 
service. 
The second great depression was of short du- 
ration, and was most severe on the 21st. On 
that day the mean minimum for the state, from 
SCIENCE. 
307 
the State-service observations, was —11.1°, 
while from those of the U.S. service it was 
+1.4°. The lowest temperature recorded by 
the State service was —31°, and by the U.S. 
service was —3.7°. These minima were re- 
corded at the same place, Columbus; the dis- 
tance between the stations being slightly less 
than three miles. It seems difficult to under- 
stand how two stations so near to each other 
could furnish results differing from each other so 
greatly. 
The question appears to be purely one of 
situation and exposure. The U.S. signal-ser- 
vice thermometers are exposed in a box or case 
of the usual form, attached to the north side 
of a stone building in the centre of the city: 
those of the State service are exposed in a 
somewhat similar shelter, but in an open space 
on the campus of the Ohio state university, 
at a considerable distance from any building. 
The conditions on the night of the 20th and 
21st were peculiarly favorable to the produc- 
tion of such a result as that given above. 
During the 20th the temperature was not very 
low ; and in the evening and night the sky was 
clear, and there was scarcely any movement in 
the atmosphere. The rapid fall in temperature 
was unaccompanied by movement of masses of 
air; and, as a result, the air confined in the 
shelter of the U.S. service thermometers was 
not displaced; and, being in contact with a 
large building which lost its heat slowly, the 
fall in temperature was not great. Had there 
been a brisk wind, or even a breeze, the result 
would have been different. The minimum of 
—31°, recorded by the State service, cannot be 
questioned ; as it was supported by numerous 
readings from ‘ private’ instruments, equally 
reliable, in the immediate vicinity and in the 
neighborhood of the city. At Westerville, 
twelve miles distant, a minimum of —24° was 
recorded by one of the observers of the State 
service. 
Nearly as great a difference was exhibited 
in the records of the 25th. For this ‘dip,’ 
which was the lowest of the three, the mean 
minimum for the whole state, as obtained from 
twenty-two stations of the State service, was 
—19.8°, while from the records of the U.S. 
service it was only —5.1°. The lowest tem- 
perature observed by the State service was 
—34°, while the lowest reported by the U.S. 
service was —15.1°. 
These comparisons lead to some conclusions 
which are certainly not without importance in 
the study of climatology. In these instances 
it appears that the U.S. signal-service has 
failed to obtain the mean lowest temperature 
