Magnetical and Meteorological Observations at Lake Athabasca and Fort Simpson (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1855 Excerpt: ... to, exhibit precisely the features described by the terms striated and serpentine; save that the vertical divisions are considerably more strongly marked than the writer is conscious of having seen them. The term cirrous aurora indicates light detached patches, scarcely distinguishable in forrn from-cirrous clouds. Lastly, auroral haze denotes a luminous appearance, usually in the northern quarter, without definite form or boundary, and sometimes also the vanishing light of other descriptions of aurora. The reference (a) is given to this appearance in the abstracts as well as to the more definite forms. The relative brilliancy is generally indicated by figures. Thus, 0' 5 represents the faintest description of aurora; 1, faint aurora; 2, moderately bright aurora, and what in low latitudes would be considered bright; 3, decidedly bright; 4, the brightest and most perfect displays. Very few exhibitions were considered to come up to the last class; of these, the principal one was not observed at Lake Athabasca, but at the Painted-stone Portage near Lake Winnipeg, on the 7th August 1843. Much of the comparative brilliancy of the displays however depends on the absence of moonlight, a circumstance which was not sufficiently taken into account at the time. The dates of the changes of the moon are given in the register for reference. The elevation of arches was observed with a wooden quadrant and plummet. The directions given are magnetical, the declination being 28 E. More or less aurora was seen on 49 out of 116 nights of observation at Lake Athabasca. There was no night, properly speaking, at Port Simpson after the lGth April, the latest date at which the sun sinks in that latitude as far as 18 below the horizon; nevertheless, the aurora was seen on twenty-fou...