Height of the Aurora Borealis.

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with which a beam darts from one side of the horizon to the opposite side, which could not happen if a hundred miles high, or upwards; by its frequently darting its beams beneath the clouds, and at very short distances from the earth's surface, and by its being acted upon by the wind.

Dalton was apt to be tenacious of his own opinions; and as the investigation of the aurora borealis had been a pet and original subject in his earlier scientific days, he fought hard for his measurements of the altitude; and did not much relish the publication of Mr Farquharson's paper as stamped with British authority. Thus in a letter he addressed to Dr Faraday (Sept. 3, 1840), he makes the following comment: "I observe the Council have voted the Rev. Mr Farquharson's paper as fit for publication in the second part, 1839. The height of the aurora was 1897 yards, or rather above one mile; I calculated it 100 to 160 miles (1828); Mr Cavendish, 52 to 70 miles (1790); Robert Were Fox, 1000 miles (1831). Surely this would be an interesting phenomenon to the British Association, whether its height was I mile or 100 miles."

Much distrust has been expressed regarding the modes of determining the height of the aurora borealis; so that Humboldt and Arago might be justified in expressing that every observer sees his own aurora, and no two men the same; the former adding that this may arise from the phenomenon of "the effusion of light being generated by a large portion of the earth at once." The Arctic voyagers had the best chance of determin-、 ing this knotty point, and much confidence may well be reposed in their observations, which went far

to contravene the measurements of Dalton. Colonel Sabine, one of the noble Arctic band, had no doubt as to the aurora occasionally resting on the surface of the sea or land; and records an instance which fell under his own observation in Skye, of an aurora, of similar character to those described by Mr Farquharson, "low in the atmosphere, having during the day the appearance of a thin mist, permitting the forms of the hills, and the irregularities of the surface of the ground, to be distinctly visible through it, and at night becoming luminous with auroral streamers proceeding from it.”

On October 3, 1794, John Dalton appeared as a member of the Literary and Philosophical Society of Manchester; a society, be it remembered, that has done good service to the cause of literature and science, not only in the manufacturing districts of Lancashire, but throughout the whole of Northern England; and on the 31st of the same month made his scientific début by reading a paper entitled "Extraordinary Facts relating to the Vision of Colours."* Nothing could be more auspicious of the rise of the young philosopher than this first appearance before a learned society, to whom he communicated an important discovery, arising oddly enough from a personal imperfection—a discovery fraught with interest in a scientific point of view, and not without material bearing on man's non-adaptation to certain callings, trades, or professions. This essay well deserves another chapter.

His residence and engagements in the "New College" or "Academy" of Manchester; his mode of life, philosophical tendencies and work; his social

* Memoirs of the Lit. and Phil. Soc. of Manchester, vol. v. part i. p. 28.

The Manchester Academy.

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and intellectual relations, are touched upon in the following letter, addressed to Elihu Robinson of Eaglesfield. It also recalls Manchester of eighty years ago, the old watchmen of the night proclaiming the hour on their different beats, and the condition of the sky, for the benefit of the sleeping lieges:—

MANCHESTER, 2 mo., 20th, 1794.

DEAR COUSIN,-Amidst an increasing variety of pursuitsamidst the abstruse and multifarious speculations resulting from my profession, together with frequent engagements to new friends and acquaintance, shall I find a vacant hour to inform thee where I am, and what I am doing? Yes; certainly one hour out of sixteen some day may be spared for the purpose.

I need not inform thee that Manchester was a large and flourishing place. Our academy is a large and elegant building, in the most elegant and retired street of the place; it consists of a front and two wings; the first floor of the front is the hall, where most of the business is done; over it is a library, with about 3000 volumes; over this are two rooms, one of which is mine; it is about eight yards by six, and above three high, has two windows and a fire-place; is handsomely papered, light, airy, and retired; whether it is that philosophers like to approach as near to the stars as they can, or that they choose to soar above the vulgar, into a purer region of the atmosphere, I know not; but my apartment is full ten yards above the surface of the earth. One of the wings is occupied by Dr Barnes' family; he is one of the tutors, and superintendent of the seminary; the other is occupied by a family who manage the boarding, and seventeen in-students with two tutors, each individual having a separate room, &c. Our out-students from the town and neighbourhood at present amount to nine, which is as great a number as has been since the institution; they are of all religious professions; one Friend's (Quaker) son from the town has entered since I came. The tutors are all Dissenters. Terms for in-students, 40 guineas per session (10 months); out-students, 12 guineas. Two tutors and the in-students all dine, &c., together in a room on purpose; we breakfast on tea at 8, dine at 1, drink tea at 5, and sup at 83; we fare as well as it is possible for any one to do. At a small extra expense we can have any friend to dine with us in our respective rooms. My official department of tutor only requires my

G

attendance upon the students 21 hours in the week; but I find it often expedient to prepare my lectures previously.

There is in this town a large library, furnished with the best books in every art, science, and language, which is open to all, gratis; when thou art apprised of this and such like circumstances, thou considerest me in my private apartments, undisturbed, having a good fire, and a philosophical apparatus around me, thou wilt be able to form an opinion whether I spend my time in slothful inactivity of body and mind. The watchword for my retiring to rest, is "past-12 o'clock-cloudy morning."

Now that I have mentioned clouds, it leads me to observe that I continue my meteorological journal, have two rain-gauges about a mile off, at a friend's house; one gauge is in the garden, and the other upon the flat roof of his house, 10 yards higher than the former. I find that the lower gauge catches 12 parts of rain for the upper II. From my correspondence with my brother, it appears they have had about twice the rain we have. I hope my friends there are not altogether disappointed with my essays; please to make the following correction, and intimate it occasionally to such as have them. Page 37-total rain at Kendal 1790, should be 62.363, and for 1791, 66.200.

Among my late experiments, have had some on the artificial production of cold, but have not been able to freeze quicksilver. I find that two parts of snow and one of common salt, mixed and stirred, produce a cold regularly of—7° or 7° below O. I have sunk the thermometer below O, in a common wine glass, half filled with the mixture.

There is a very considerable body of Friends (Quakers) here; near 200 attend our first-day (Sunday) meetings. I have received particular civility from most of them, and am often at a loss where to drink tea on a first-day afternoon, being pressed on so many hands. One first-day lately, I took a walk in company with another to Stockport; there are but few Friends there, but the most elegant little meeting-house that can be conceived; the walls and ceiling perfectly white; the wainscot, seats, gallery, &c., all white as possible; the gallery rail turned off at each end in a fine serpentine form; a white chandelier ; the floor as smooth as a mahogany table, and covered with a light red sand; the house well lighted, and in as neat order as possible; it stands upon a hill; in short, in a fine sunny day it is too brilliant an object to be attended, by a stranger at least, with the composure required, JOHN DALTON.

CHAPTER VI.

ON DALTON'S COLOUR-BLINDNESS.

"Oculus ad vitam nihil facit, ad vitam beatam nihil magis."-SENECA.

Or,

"The eye, no servitor of duty,

But minister of all life's beauty."

JOHN DALTON, passing a shop-window in Kendal, saw a pair of stockings prominently marked "Silk, and newest fashion," and

having examined their texture, bought them as a fitting present for his mother, whom he knew to be acquainted only with knit yarn and home-made sorts. On his next visit to Eaglesfield, the compliment of the stockings was duly made, and elicited the following exclamation from Dame Deborah :— "Thou hast brought me a pair of grand hose, John, but what made thee fancy such a bright colour? What, I can never show myself at meeting in them!" John was disconcerted by the maternal comments, as the colour of the said stockings appeared to his eyes a bluish dark drab, and quakerish enough in all verity. "They're as red as a cherry, John!" But John could not see this, nor could brother Jonathan, who was also present; so there were two to one in the dispute, and poor Deborah left in the minority. Being firm in her opinions she called in her neighbours,