6o 



PROCEEDINGS OF THE CANADIAN INSTITUTE. 



and small, are duly registered upon this instrument. You see by this chart for 

 8 a.m. of the 28th that the centre of the storm which is causing these violent lake 

 undulations is over the State, of Florida, a distance of 1,300 miles from Toronto. 



FIG. 4. 



The lowest isobaric line, when drawn to tenths of an inch within this disturbance, 

 was only 29.90, but owing to this time of year being favourable for the northerly 

 movement of West India hurricanes, a careful watch was kept upon it by our 

 forecast officer, who, finding after completing the 8 p.m. chart a slight development 

 of this depression, warned all our lake stations for a heavy easterly gale. This chart 

 for 8 a.m. of the 30th of September shows how the storm centre travelled slowlj^ 

 but directly to the lake region, where it caused a severe gale and a heavy general 

 rainfall. To illustrate the value these lake instruments are likely to prove when 

 studied in conjunction with the daily weather chart for assisting in the successful 

 forecastirtg of precipitation as well as wind storms, let us examine the chart for 

 8 p.m. of the 19th of January last. Approaching the lake region from the north- 

 west is a well-defined low area (centre about 29.70), while to the far south-west 

 there is what appears to be a minor depression (centre about 30.00). Under such 

 conditions it would be of great value to know if this latter area were going to develop 

 and move towards us, as then it would be an easy matter to predict easterly winds 

 with precipitation for the lake region, while, on the other hand, one would base 

 their prediction upon the approaching north-west low, which usually gives southerly 

 winds and fair milder weather. In this case, upon looking on the chart for 8 a.m. 

 next day, you will observe the south-western low had developed, and was rapidly 

 moving up the Mississippi valley, while the north-west low was quickly dispersing. 

 The 8 p.m. chart for the 20th shows a still further development of the southern low, 

 which has moved to the State of Ohio (centre, 29.70), while the northern depression 

 appears to have completely dispersed, or to have been absorbed by the former. At 

 4 p.m. of this day it began to snow, and' continued till next morning, when over six 

 inches had fallen at Toronto, and a general snowfall prevailed throughout the lake 

 region. A few days later, upon receiving the Humber records, marked abnormal 

 oscillations were noticeable during the night of the 19th ; also similar but minute 

 undulations were found upon the Observatory photographic barograph trace. These 

 records prove that, although the surface air was moving from the south, the upper 

 or boundary surface of the lower air was rapidly moving southward, that is, in 

 opposition to the superincumbent upper poleward current, therefore causing atmos- 

 pheric waves or billows upon its boundary surface of sufficient magnitude to 

 disturb the air nearest the earth. These lake records appear to prove conclusively, 

 some time before the ordinary mercurial barometer and direction vane showed the 

 change, that the southern low area was developing and the northern one dispersing. 

 As the atmospheric conditions for the next few day's are very much disturbed, and 

 are followed by a most pronounced anti-cyclone and great cold in the North-west 

 Territories, which eventually extended to the lakes, we shall look at a sequence of 

 weather charts in conjunction with some very interesting Humber records. As 



