On the Construction of Meteorological Instruments. 239f 



spections in the course of the day^ the atmospheric temperature^ 

 and (on the principle of the late celebrated Dr Hutton) its hu^ 

 midity, for every hour- of the day and night, could be readily 

 and exactly determined. For a particular account of this ne^ 

 mode of constructing a meteorological apparatus, the reader is 

 referred to the last volume of the Transactions of the Royal So- 

 ciety. The present notice is chiefly confined to an explana- 

 tion of the figures, Plate IV., where certain forms of 'construc- 

 tion are represented, and which will render the practical appli- 

 cation of the principle easily apprehended. 



The possession of a single thermometer, constructed on this 

 principle, renders the keeping of an accurate thermometrical re*, 

 gister a comparatively easy task, as the observer is freed froift 

 the irksome necessity of being always at home and disengaged 

 at certain fixed hours. This freedom, be it also observed, is at- 

 tainable at a very trifling ex pence ; and at a very small addi- 

 tional expence, two thermometers and hygrometers may be thus 

 constructed, and by means of these, an accurate and valuable 

 register may be kept with very little inconvenience. In compa^ 

 rison with the usual method, it would be found an agreeable 

 amusement rather than a labour, tolerable to very few, and easy 

 to none. 



Eocplanation of Plate IV. 

 Fig. 1. Represents an apparatus applicable to various pur- 

 posesj and, among others, that of ascertaining the tempe- 

 rature, or the temperature and humidity, of the atmosphere 

 every successive hour of the day and night. For this purpose, 

 only three inspections in the course of the day are requisite ; 

 for example, at 7 a. m., 4 p. m. and 11 p. m. 



a, Seven thermometers suspended on rollers or hinges ; four are 

 in one row in front, and are represented in their vertical po- 

 sition ; the other three are suspended about an inch and a-half 

 behind these, and are seen in their horizontal position. 



These thermometers are, on the present occasion, supposed to be 

 made with old, colourless, and carefully filtrated spirit, that 

 has been deprived of air. The index may be very minute, 

 and, consequently, the bulb small, which last is an important 

 consideration. The tube should admit of the spirit rising to 

 about 140° Fahrenheit, though it may be unnecessary to di- 

 vide the scale much above 100». 



