450 Professor Young's New Criteria 



Dec. 29. — Last night a gale, continuing in the morning; 

 wind west-south-west. The fall in the barometer at the com- 

 mencement was not more than one-tenth of an inch, and du- 

 ring the night it did not fall at all, standing during the gale 

 at 29*9. Thermometer yesterday morning at 34°, with a hard 

 frost on the ground, which lasted till 11 o'clock a.m. At 10 

 o'clock p.m. thermometer was 48° (a difference of 14°), and 

 this morning at 50°. 



Dec. 30. — Last night, but more particularly from 3 o'clock 

 this morning, very heavy gusts of wind nearly west, without 

 any rise or fall in barometer worth notice ; but the tempera- 

 ture at night was 50°, and at half-past 7 o'clock this morning 

 52°. About half-past 6 o'clock in the morning I thought I 

 saw patches or gleams of electric light along the grass. Gale 

 continued throughout the day, barometer rising very slowly. 



Dec. 31. — Same storm continued all last night, with ther- 

 mometer at 54° at half-past 10 o'clock p.m., and at 56° at 8 

 o'clock this morning; barometer did not vary more than half 

 a tenth, standing still at 30°. A drizzling rain and damp at- 

 mosphere so much illuminated that 1 could see my watch at 

 any hour, though there were no stars and the moon at the 

 change. I observe in the papers an account of a very ex- 

 traordinary thunderstorm, doing much damage to houses and 

 cattle at Ballyshannon, on Friday the 30th. 



In the evening of the 31st it became calm and the air cooler; 

 weather continued very fine for two or three days. 



1843. Jan. 13. — Last night barometer fell seven-tenths of 

 an inch between 11 o'clock p.m. and 8 o'clock this morning 

 (nine hours), when it was lower than I had almost ever seen it, 

 except in Jan. 1839. A very heavy squall of wind and rain 

 during the night, wind veering from south-east to south or 

 south-west. Morning calm, but showers of snow during the 

 day, and from 8 o'clock p.m. the wind began to blow a gale. 

 I have heard from Dublin that the barometer was so low as 

 27'9, and I see in our own papers notices of an extraordinary 

 state of the tides. 



LV. New Criteria for the Imaginary Roots of Numerical 

 Equations. By J. R. Young, Professor of Mathematics in 

 Belfast College*. 



IN a former Number of this Journal, and with fuller detail 

 in a more recent publication f 5 I have discussed some 

 useful formulae for discovering imaginary roots in an equation 

 from inspecting the coefficients of its terms. The new forms 



* Communicated by the Author. 



t Researches respecting the Imaginary Roots of Equations. 



