PROCEEDINGS OF THE CANADIAN INSTITUTE. 



59 



and, as you will observe, in the second one they are of such a regular character as 

 to be commonly termed " roll cumulus." 



Let us now examine the Burlington and Huniber records for the 4th of 

 October, 1896 (Fig. 3), during fine settled weather throughout the continent, 

 plotted upon the same time sheet. As previously mentioned, these squares, when 



FIG. 3. 



measured vertically, correspond to one inch change of water level, and, harizontally, 

 to every fifteen minutes of time. It is interesting to note, not only the marked coin- 

 cidence of these undulations, but the agreement of their time intervals, viz. : 22.8 and 

 22.0 mins. The greater amplitude of the Humber trace is due to the configuration of 

 the adjacent shores and shallowness of the Bay. To obtain an idea of the prevailing 

 atmospheric conditions, let us look at the morning and evening synchronous weather 

 charts for this day. At 8 a.m. you will observe an important high area over North- 

 ern Ontario, while to the west of Lake Superior there is a well-defined area of low 

 pressure. The weather is fine, and the direction of the wind northerly, throughout 

 the lake region, but immediately to the westward the winds are from the south- 

 ward. At 8 p.m. the high area has moved eastward, while the western low is dis- 

 persing over Lake Superior. As the winds have become southerly, the upper and 

 lower strata of air are moving approximately in the same direction, therefore, 

 according to Helmholtz, the upper atmosphere should be in an undisturbed condi- 

 tion. As a fair type of rapid undulations upon the lakes, during light winds and 

 fine weather preceding a severe storm, let us take the Humber and Burlington 

 traces from 8 a.m. to 3 p.m. of the 28th of September, last (Fig. 4)- Here, again 

 you will observe a decided coincidence between the two traces, and a wonderful 

 agreement of time intervals, being 14.4 and 14. i minutes respectively : also, the 

 oscillations are much more rapid than when precedins: settled weather. The move- 

 ments upon the Humber instrument appear to be about double those upon the 

 Burlington one. On the latter trace at t p.m. a peculiar rapid rise and fall of over 

 an inch is seen, due to the passage of the Hamilton boat. In fact all vessels, large 



