DESCRIPTION OF A HYGROMETER. 



61 



try ; z, the dairy ; A:, water closet ; /, open 

 porch ; w, cow-house. 



The estimated cost of this building in 

 J:ngland is £232 7s. 3d.; and it may be 

 built in many parts of this country for less 

 than $1000. The tower contributes much to 

 its picturesquoness ; and in certain localities, 

 and for some purposes, it would be highly ap 



propriate and picturescpe ; while in others 

 it would have too much pretension. In cases 

 where the latter objection would apply, by 

 omitting the upper story of the tower, and 

 finishing it like a gable in the main roof, a 

 less picturesque but still pretty cottage would 

 be the resul. 



J. W. Wild. 



DESCRIPTION OF A HYGROMETER, 



FOR REGULATING THE MOISTURE OF THE AIR IN CLOSED APARTMENTS. 



Mr. Downing — I send you herewith a wood 

 cut of the hygrometer, about which you in- 

 quire, together with a description of it, ori- 

 ginally furnished for the Journal of the Frank- 

 lin Institute. 



In a letter of Franklin, addressed to Ed- 

 ward Nairne, of London, a plan for a hy- 

 grometer is men- ^ — ^ 

 tioned, which was ' A 

 afterwards made 

 by Mr. Nairne, 

 and is described 

 in vol. iv, page 

 449, of Sparks' 

 edition of Frank- 

 lin's Works. 



In this instru- 

 ment the motive 

 power is derived 

 from a slip of 

 wood, one end 

 of which is fixed, 

 and the other end 

 attached to the 

 short arm of a 

 bent lever, which 



is moved by the expansion and contraction of 

 the wood, the extent of the motion being 

 shown upon a graduated arc at the extremity 

 of the lever. 



Having found that a hygrometer resem- 

 bling this, which I have used for several years 

 past, is very readily affected by changes of 

 moisture, I have made one upon a similar 

 phin, and attached to it an apparatus which 

 will produce any required degree of moisture 





w 



Fig. H. — Batchelder''s Hygrometer. 



in the apartment in which it is placed. An 

 instrument of this kind will not indicate the 

 dew-point with accuracy, neither can two in- 

 struments be made to give precisely the same 

 expansion or contraction when exposed to the 

 action of the same degree of moisture ; it is, 

 therefore, of no value for observations that are 

 to be recorded and compared with each other, 

 but each instrument, when used in conserva- 

 tories, or in any place where the temperature 



