DESCBIPTION OP AN IMPROVED HYGROMETEE. SQS 



wire tightly around it from left to right : this screw 

 should be fourteea or fifteen threads in length ; the end 

 of the axis, f, is divided, and is to be closed by a small 

 sliding ring. As this is the most important part of the 

 Hygrometer, fig. 2 represents it on an enlarged scale. 



A hop and drop (fig. 3) is made of fine gold wire, 

 of such a size as that when suspended on the screw, it 

 may slide along it with perfect freedom by means of the 

 revolution of the axis, but not escape from one interval 

 to another by any other motion : should the loop, on 

 trial, be found too large (as indeed it ought to be) it 

 may be easily closed a little, by placing it on the screw, 

 and pulling it gently by the drop ; it will then assume 

 an elliptical form, as in the figure. This loop is in* 

 tended to register the number of revolutions made by 

 the index, as it hangs freely from the i^.m, and advances 

 one interval between the threads of the screw, for each 

 revolution. 



The Index, g h, is made of fine ivire, accurately 

 balanced, and as light as possible ; it fits on the end of 

 the axis e, and is to be phced at right angles iiith the 

 commencevient of the serein, (See fig. 2.) 



The beard of the ooheena hooloo is represented at f d, 

 (tig. 1.) The top of it, which is crooked, being cut 

 off, it is first secured between the cheeks of the axi?, 

 at f, by means of the small sliding ring; the axis is 

 then turned round till the gold loop is brought to the 

 fifth or sixth interval o( ihc jv/ti:-, counting from the 

 dial plate ; the screw at c is then advanced, so as to 

 receive the lower or thick extremity of the beard of the 

 oiibcena hooloo in the notch, where it is also confined by 

 the sliding ring d. 



