64 REPORT — 1861. 



Description of a Mercurial Barometer, recently invented ii/ Mr. Richard Howson, 

 Engineer of Middlesborough-on-Tees. By Petee J. Livset. 



This barometer consists of a straight tube, called in this paper "the tube," similar 

 to that used for the common straight barometer, but somewhat longer, and a 

 hollow stalk nearly the same length as the tube, but of such smaller diameter that 

 it will pass up the bore of the tube and leave an annidar space of about jijth or ith 

 of an inch. The lower end of the stalk is smTounded and united with a shoi-t tube 

 called "the cistern," sufficiently large in diameter to allow the tube to pass into it 

 and leave an annular space. When the barometer is in working order, "the tube " 

 is suspended freely in a vertical position with its open end downwards, the stalk 

 passing up the bore of the tube till the lower end of the tube enters the cistern ; and 

 the anmdar spaces between the stalk and interior of tube, and the stalk and cistern, 

 are filled with mercury, the cistern containing sufficient mercury for the immersion 

 of the lower end of the tube when the stalk and cistern are at their lowest position. 

 The tube and cistern are filled with niercm-y to form a vacuum at the upper end of 

 the tube, so that the pressm-e of the atmosphere alone will sustain the weight 

 of the stalk, cistern, and mercmy. 



The stalk has a buoyant power sufficient to carry its own weight, the cistern, 

 and the mercmy in the cistern, at the lowest pressiu-e of the atmosphere. The 

 pressure of the atmosphere will be shown by this bai'ometer, by the difference be- 

 tween the level of the mercury in the cistern and that in the tube, by the position 

 of the top of the column in the tube, and by the position of the stalk and cistern. 



Barometers may be made upon this principle, having a long range or movement 

 for a small change of pressiu-e, by which such changes may be measm-ed with great 

 delicacy ; and this advantage, without the inconvenience of a very long scale, may 

 be obtained by using weights which can be added or removed as requhed for, say, 

 the whole inches, reading the fractions of the inch ft-om the scale. 



One advantage of this barometer is the comparatively small quantity of mercury 

 required. Tubes of large diameter may therefore be employed, and thus instruments 

 having great power and accm-acy may be obtained, as a small change of pressure 

 will be multiplied by the large area, and the power or change of pressm-e acting to 

 produce a movement in the barometer will thus be gi-eat in proportion to the fric- 

 tion resisting the movement. 



The formula for calculating the rise of the top of the column of mercury in the 



TP 



tube for any given increase of pressure is R=-p--t-P- 



The formula for the movement of the cistern for any given rise, when the mer- 

 cury extends above the stalk and fills the entire bore of the tube at the lowest 



• TP 



pressure, is R=-p ; but when the stalk extends above the colimin of mercury and 



into the vacuum space, it is E. = — ^ The increase in the depth of the cistern 



is obtained by the foi-mula E = D - R ; when the top of the stalk is always below 

 the mercury and it fills the entire bore of the tube, the depth of the cistern is uni- 

 form for all pressm-es. In the above formula R is the total rise of the top of the 



column in the tube for any given increase of pressure, R rise of cistern, R rise of 

 level of cistern, T area of the bore of the tube, G area of the glass or material pro- 

 ducing displacement in the tube, P pressui-e in inches of mercury, C area of cistern, 



C area of cistern minus G, T area of annular space between interior bore of the 



TP 



tube and the stalk, D=--,— •. In these formulae it is supposed that the tube, stalk, 

 G 



and cistern are perfect tubes or cylinders uniform in area throughout their entire 



lengths. 



On the Great Cold of CJiristmas 1860, and its destructive Effects. 



By E. J. Lowe. 



The author said that the excessive cold of Christmas 1860, near Nottingham, being 



