Registering and Printing Barometer. 



11 



more than three times the barometrical pressure. It 

 would have been an easy matter to adapt the second screw 

 and cog wheel, so that the curve would be exactly an 

 integer scale — say 1, 2, 3 or 4 times ; but as our printed 

 results may be obtained much more accurately, and as 

 often as is necessary, it was not thought of sufficient im- 

 portance to construct a screw especially for this purpose. 



"We will now explain the mechanism for printing the 

 results. 



A sectional view of the combination is shown in fig. 4, 

 where x and y are two vertical steel axles. The final 

 result expressed in thousandths of an inch, is found on the 

 axle x, where u is the units wheel, t tens, and h the hun- 

 dredths ; or where the thousandths of an inch is the unit 

 of measure, u will represent thousandths, t hundredths, 

 and h tenths of an inch. 



Fie. 4. 



u iliiiliiiiiiitiiimm 



t 



I 



'III 



111 





II II 



1 



1 



(50) 



liinmimi 



imnmn 



Tl li 









1 



I 





The wheel u Q may be supposed to have ten teeth, and 

 is connected with it, so that they move together. If mo- 

 tion be given to u Q , so that it move one tooth at each 

 impulse, each tooth will represent the ^Vs- of an inch ; 

 and ten impulses, or a whole revolution, will represent the 

 of an inch. The wheel u has one tooth, and the 



