254 



THE CANADIAN INSTITUTE. 



[1854. 



serrated or jagged, the light of the sun shining between the 

 teeth. These teeth or projections appear to increase in size, and 

 to diminish in number, until on some occasions the two discs 

 have been seen united only by broad, well-defined dark threads,, 

 which at last disappear instantaneously. The same phenomena 

 recur in an inverse order as the eastern limb of the moon ap- 

 proaches the eastern limb of the sun. It should, however, be 

 noticed that the threads above mentioned are considered by Arago 

 to have been optical delusions, arising from the axis of the tele- 

 scope not having been properly pointed. 



In the second class of observations are included the changes 

 occurring in the intensity and quality of the sun's light and heat, 

 and the atmospheric or terrestrial phenomena produced thereby. 



Observations should be made continuously throughout the 

 eclipse with the ordinary psychrometer, or wet and dry bulb 

 thermometers, in the shade; and, in the absence of an actino- 

 meter to measure the intensity of heat produced by the sun's 

 rays, valuable information will be given by a common thermo- 

 meter with a blackened bulb (a coating of lamp-black will serve) 

 fully exposed to the sun's rays, and protected as much as pos- 

 sible from reflection of heat from any neighbouring buildings or 

 substances. 



It would be desirable to obtain some measure of the variation 

 in the intensity of the sun's light; but no plan has yet been de- 

 vised for doing this; the methods rudely practicable in a total 

 eclipse will be here of little avail. 



Changes in the quality of the light should be noted by obser- 

 vation of the solar spectrum formed by refraction through a prism, 

 • examining whether any of the colours seem more changed in 

 intensity than others,, and whether the red end of the spectrum, 

 appears to increase; also, if the prism be capable of showing the 

 dark lines, whether they undergo any modifications either in 

 number or position. It would also be interesting to take photo- 

 graphic copies of the spectrum at different stages of the eclipse, 

 to detect any variation in the actino-chemical raj-s. If the ob- 

 server be provided with a polariscope or a Nichol's prism, lie 

 should examine the polarisation of the light at different jjointsof 

 the sun's disc. 



II. One observer should also confine his attention to pheno- 

 mena which do not require instruments for their observation. 



Among these, the most important will be to note if any 

 change be perceptible, about the period of the greatest obscura- 

 tion, in the aspect of terrestrial objects, and especially in the colour 

 of the sky near the horizon in the part opposite to the sun: to 

 observe whether a well-defined shadow of a staff or cross thrown 

 on a wall be subject to any flickering motion, especially about 

 the edges; and whether any moving bands or patches of light 

 are seen to traverse the wall or ground; also, whether the sha- 

 dow of the moon can be detected " sweeping through the air," as 

 described by Mr. Airy in the last total eclipse. 



Another observer should confine his attention at this period 

 to the sun itself; examining how the intensity of the light varies 

 in different directions round the disc ; whether there are beams 

 of light, or the rudiments of a ring round the moon; and whether 

 there is any light on the side opposite to the bright lune. 



In the event of a light cloud or haze crossing the sun, the 

 observer should watch for any manifestation of corona? or co- 

 loured rings, noting their colours and approximate diameters. 

 They will be most easily seen by reflection in water, or by the 

 use of a light brown o-lass. 



It is not to be expected that the effects described as produced 

 on the animal and vegetable creation by the entire deprivation of 

 the sun's light in a total eclipse will be at all noticeable in the 

 present case, nor that stars will be visible to the naked eye. It 

 is, however, possible that the planet Mars may be caught sight 

 of, about 90° to the east of the sun. 



In conclusion, observers should be warned against attempting 

 too much. The period of the greatest obscuration only extending 

 over three or four minutes, it is impossible for a single observer 

 to note all the phenomena that oecur. The bestway will be for 

 several persons to agree beforehand on the points to which the 

 attention of each shall be exclusively directed, and from which 

 no temptation should be suffered to distract him. 



As a rough guide to the circumstances of the eclipse at dif- 

 ferent places in Canada, it may be remarked that a line drawn 

 on a map from Ogdensburgh to Isle Koyale, on Lake Superior, 

 will pass through those places at which the eclipse will be cenj 

 tral. Lines parallel to this drawn through the south-western 

 extremity of the Island of Montreal and through Kingston will 

 be respectively the northern and southern boundaries of the 

 annulaiity. Parallel lines through Toronto and Quebec will 

 approximately determine those places at which eleven digits 

 will be eclipsed at the greatest obscuration. 



The times of the beginning of the eclipse will be, at Toronto, 

 3 h 44111.7; at Kingston, 3 h 57™ ; at Ogdensburgh, 4 L 2 m -V; at 

 Montreal, 4 h ll m "3: at Quebec, 4 11 19™, the angle of contact 

 being about 150° from the north point toward the west. The 

 duration of the eclipse will be nearly two hours and a half. 



In order that observations made in accordance with the above 

 suggestions may be presented in a combined form to the Insti- 

 tute, it is requested that any communications on the subject be 

 addressed to the Director of the Magnetic Observatory, Toronto. 



INCORPORATED BY ROYAL CHARTER. 



JPifteeaatSi Ordinary Meeting April lst 9 1S54* 



The following gentlemen were elected members: 



J. S. Walker Brantford. 



T. Maclear Toronto. 



H. Piper " 



