win 1 I II i; M()Mi;ii.i;s \ i; i , cia i ,i; \i.i,') i nacci i; \ tk 



The iiroMcni oi .•iccm-.-icy in I litrinoiiicli rs \\;is Ihcii stalid 1)\' 

 Ihc uriUr' as fdllows: ••I'Imt.- ,iir liner rc.-isnns ^^\n .1 



I lii-i-iii(iiiicl IT is iii.iccii i-,i I (■ when il 

 ni'i lin.'i I'ilv 1 (■ .'I \ (■ s I lie iii;i kcr's 

 li.iiids, (I'"irsl), iiii]irn|icr scisuii- 

 ini;- (iT Hie fz'l.iss <•! Ili<- I hcniiolii- 

 clc.' Iiilic, (Second), I'rcc/.ilifr-poinI 

 nl' I licrirKMiicIci- niil clctcniiincd, 

 :ind ('I'liii'd), llirnniiiiirl cr nol (•;ili- 



l.r.ilcd. 



^^ 111 

 il h.n 



licrniDiiiclcr tiihcs 

 (■II siiniciciit l\' sc.'i- 



simcd. (Jl;iss, like \\o()(l, lui.s lo he 

 treed t'roin sliriiiUafrc If uiisea- 

 sdned filas.s is used, tiie liore will 

 (■(iiilraft with age and llie llier- 

 iiionictcr will read liigh. 



"Second. Ihe tlicrmoiiietcr may 

 nol have been tested at the freez- 

 ing-])oint. Not one thermometer in 

 a dozen is ever tested exce]it at 

 the freezing point and few such in- 

 struments are ever tested at all. 

 In the jioorer grade of instruments, 

 onee this i32-degree mark has been 

 foimd, the tube is fastened to the 

 metal back and the thermometer is 

 jilaeed on sale. 



"'I'liird, the inequalities in the 

 diameter of the bore may not have 

 been determined. From the nature 

 of the glass-blowing operation, the 

 bore of a thermometer-tulie has 

 many and often considerable irreg- 

 ularities, necessitating careful cali- 

 bration. Even the best of ther- 

 mometers possess these errors in 

 the diameter of the tube. To 

 obviate these inherent character- 

 istics, the following method of grad- 

 uation is resorted to in making a 

 standard thermometer: A carefully 

 annealed glass tube is selected and 

 a small thread of mercury, five de- 

 grees in length, is inserted in the 

 tube and this is pu.shed along the 

 length of the bore and the gradua- 

 tions marked on the tube itself 

 with a diamond. Afterwards the 

 thermometer is tested in compari- 

 son with a known standard and 

 the temperatures at 32 degrees and other definite heights are marked. 

 To complete the operation, in case the instrument is to be used for 

 purposes requiring great accuracy, as in testing other thermometers, 

 the thermometer is further compared with a standard and corrections 

 noted, whenever necessary, for every degree throughout the length of 

 the tube. 



True Tempera- 

 tures (Corrected 

 temperatures) 



Incorrect Tem- 

 peratures (Tlier- 

 mometer scale) 



Fig-. 1 — E.xaggerated Thermome- 

 ter Tube — If an ordinary tliermom- 

 eter tube could be inagnified, the 

 irregularities of the bore would 

 look something like this. The 

 maker stamped graduations on the 

 scale regardless of the diminishing 

 or increasing size of the inside of 

 the tube. This resulted in the 

 thermometer being 3° too low at 

 40°, and 4° too high at 20 degrees. 

 (Courtesy, California Citrograph) 



-;Cal. Citrograph, Vol. 6, Pp. 3-.; 



22 



