of Edinhurgh, Session 1882 - 83 . 
55 
vicinity for periods of twenty-four hours did not form a trustworthy 
index of the success of a prediction. If observations could be made 
twice' or three times a day, so that each prediction would cover a 
shorter time, and if the intensities of the rainband in different 
directions were compared each time, much more decided proofs of 
the utility of the spectroscope as a short-period predictor might 
reasonably be expected. Situation and circumstances rendered it 
possible only to make an observation on the north-west sky each 
morning at 9 a.m., hence all the results described in this paper are 
deduced from observations in that direction at that hour. If 
possible the observation should be made on a piece of clear sky, but 
the spectrum of the light from clouds is not necessarily untrust- 
worthy. Out of 120 consecutive predictions 75 percent, of those 
made on a clear, and 73 per cent, of those on a cloudy, sky were 
verified. The spectroscope cannot be used in a thick mist or a snow- 
storm, and its indications in frosty weather are usually too faint to 
be of much value, although it may almost always be relied upon 
to predict a thaw at least one day beforehand. 
Remarks on the Chart for January 1883. 
During the .month of January 1883 the barometer and thermo- 
meter were observed as well as the spectroscope, and the accompany- 
ing chart embodies the results obtained. 
The shading in the upper half of the column allotted to each day 
represents the prediction, that in the lower half shows the degree of 
fulfilment. When the upper half is blank {e.g., the 2nd) no rain ” 
was predicted, and a blank lower half {e.g., the 4th) shows that no 
rain fell. A very light shading in the upper half {e.g., the 3rd) 
denotes a prediction of “probably a little rain,” slightly darker 
{e.g., the 5th) means “some rain,” while the very dark (as on the 
1st) stands for “rain.” The lower half shows the rain which 
followed up to 9 p.m., the length, position, and darkness of the 
parts shaded representing approximately the duration, time, and 
heaviness of the showers. Snow is shown by peculiar shading, 
as on the 27th. The first and second curves join the points at which 
the barometer and thermometer stood each morning at 9 o’clock, 
and the third exhibits the intensity of the rainband in a similar 
manner. A rise in this curve corresponds to an increase in the 
