1854.] 



DESCRIPTION OF SANG'S PLATOMETER. 



305 



I cannot refrain from also quoting the following paragraph 

 from the same paper, as much to the point : — 



"It appears unquestionable that the phenomenon of the 

 Seiches is due to an unequal pressure of the atmosphere in 

 different parts of the Lake at the same time, i. e., to the simulta- 

 neous effects of columns of air of different weight, or different 

 elasticity, arising from temporary variations of temperature, or 

 from mechanical causes;' and if such be the case, all Lakes of a 

 certain extent, and even inland seas, must be subject to the same 

 influence, and therefore present the same phenomenon ; and I 

 have little doubt that correct observations will verify the pre- 

 sumption."* 



With respect to the irregular tides observable in the Baltic and 

 Black Seas, and other great bodies of saline water of a similar 

 character, it will be sufficient to give the following, regarding the 

 first-named sea, from a standard geographical work, as bearing 

 intimately on the subject under discussion : — "The Baltic being 

 a close sea, is of course not subject to the phenomena of regular 

 tides. But though such be wanting, a variation in the height 

 of its waters, equal, frequently, to 3^ feet Swedish, is observed 

 at irregular Intervals. This occurs at all seasons, but chiefly in 

 the autumn or winter, at the time of heavy rains, or when the 

 atmosphere is charged with clouds, though unattended with fall- 

 ing weather. The water maintains its height frequently for several 

 days, sometimes even for weeks. Prevalent winds, flooding rains, 

 melting snows, and many other causes were assigned for this 

 very remarkable phenomenon ; but it continued to occur, inde- 

 pendent of all these, till 1804, when. Schulten, a Swedish physi- 

 cian, after having collected all the observations that had been 

 made, found 'that the greatest height of the water corresponds 

 with the greatest depression of the barometrical column ; and 

 conversely.' The almost total absence of oceanic action in this 

 sea leaves the cause thus assigned to operate with full power; 

 and if Schulten's hypothesis be confirmed, of which there is now 

 but little doubt, it will, in all probability, serve to explain similar 

 phenomena observed in other close waters, as the Caspian, Lake 

 Balkai, and the Lake of Geneva, to which Saussure has assigned 

 similar causes."f 



To conclude. Having at last completed my retrospect of the 

 state of the interesting philosophical questions which have so 

 long engaged my attention, and having, in so doing, far exceeded 

 the limits which I had prescribed to myself when I first ventured 

 to press upon the Institute the establishment of a series of ob- 

 servations on the rise and fall of our noble Lakes, combined with 

 that of a system of simultaneous meteorological observations 

 throughout the country, it will not be wondered that I should 

 bring my desultory remarks to an abrupt close. Reserving, 

 therefore, any further expression of opinion until the fate of my 

 proposal shall have been decided, I shall at present only add an 

 earnest entreaty that, whatever may be the humble merits of the 

 discursive review which I have taken of the important subject 

 under discussion, it will at all events be received with indulgence; 

 and that the Institute will be induced to take the trouble of pa- 

 tiently separating whatever grains of value there may be among 

 the chaff, and manfully continue to do its duty to itself, to Bri- 

 tish Canada, and to the scientific world at large, until it shall 

 have satisfactorily accomplished the indisputably laudable pur- 

 pose in view; — ever watchfully bearing in recollection that, in the 

 present singularly emulative age, the onward march of mind and 

 enterprise, though fitful, is often found to advance with giant 



* See Canadian Journal, Vol. II., pp. 27, 28, &c. 



t See M'Culloch's Geographical Dictionary, Article Baltic. 



strides,more akin to the sudden movement of the whirling rail-car 

 and the electric wire, than to the slow-paced action of by-gone 

 times — as, witness the late rapid extension of netwoiks of rail- 

 roads through almost every civilized country, and the long 

 doubtful completion of marine electric telegraphs in addition to 

 those by land — the spanning alike of mighty rivers and yanning 

 chasms with vast, yet airy, ribbon-like, suspension-bridges — the 

 construction of a class of stately yet swift iron clippers, nearly 

 equalling steamers in their speed, and of leviathan screw 

 ships ofl 0,000, nay 20,000 tons burden, rushing through the 

 waters at the astounding rate of upwards of 400 miles a day — 

 the successful sounding of the great ocean at the depth of 

 more than two miles — and, though last, perhaps not least in in- 

 fluence, the almost simultaneous discovery of gold-regions in dif- 

 ferent parts of both hemispheres, including even our own youth- 

 ful favoured land! And therefore, while Conventions of learned 

 and scientific delegates from among the chief nations of Europe 

 are being assembled to adopt measures for the universal extension 

 of " the science of Physical Geography," and the completion of 

 a girdle of meteorological observations over the whole ocean, as 

 well as every terrestrial region of the globe,J and our energetic 

 and intelligent "go-a-head" American neighbours are being- 

 most forward in the noble mental strife, it would little redound 

 to the credit of Canada to be found standing listlessly aloof, 

 with folded arms, while so important a gap in the chain of 

 philoshphic research remains to be filled up at its very door. 

 Let, then, the Canadian Institute, as a leading British-American 

 Association, be " up and doing, while it is yet day,'' bearing in 

 mind the remark of an eminent British soldier and statesman — 

 that he that tries and fails, has at least the chances, of war to 

 urge in his defence; while he that is content with looking on at 

 a distance and doing nothing, only registers thereby his own in- 

 efficiency and imbecillity. 



i See the able and interesting address of Lieut. Maury, of the American 

 Navy, at the late annual meeting of the New York Geographical and Sta- 

 tistical Society, held on the 10th of February last. 



Description of tlie Platometer 9 an Instrument for calculating 



tile Area of Figures drawn on Maps. Invented by 



Mr. Jolin Sang.— With Plate. 



The instrument is represented in Fig. 1 of the plate. It con- 

 sists of a heavy brass frame A, carrying the journals of an arbor, 

 on which are fastened the cone C, and the two rollers BB. The 

 rollers are of equal diameter, so that when they are moved over 

 the map, the frame A is carried forward or backward in a 

 straight line. In the edges of the frame there are cut two 

 grooves, which receive the rims of four friction wheels, two of 

 which, W W, may be seen in the drawing. These friction 

 wheels are journaled in a light frame F, to which the tracing 

 point P is firmly attached; a handle, H, is also attached to the 

 frame F, by means of a universal joint. A third frame, /, is 

 connected with F, by means of a centre point hinge, and it car- 

 ries the journals of an index wheel I, the very narrow edge of 

 which, by means of two springs, is made to press on the cone. 

 There is a ring of silver on the index wheel, divided by lines and 

 figures, which are read off by a vernier and by a reading glass 

 R, both fastened to the frame/. The frame / is also provided 

 with two screws, the heads of which are shown in the figure 

 (one of them near the letter/), giving the means of adjusting 

 the height of the index wheel, so that the line in which it touches 



