516 



III. Die Vergleichung bei der Norrnal-Aichungs-Kommission in Berlin 

 wurde noch vom December 1869 bis Januar 1870 fortgeführt und ergab, wenn wir die 

 unter II. gegebene Gleichung für Nr. 1605 in mm ausdrücken: 



P.L. = 1 m -}- 0,212 mm + 17,7''-^; da die einzelnen Vergleichungen ergaben: 

 P.L. — 1605 -= + 0,243 mm bei -+- 8,5*' Gels, (am 29. Januar 1870) 

 P.L. — 1605 = + 0,248 mm bei -\- 11,2° Gels, (am 8. December 1869) 

 P.L. — 1005 = 4- 0,246 mm bei + 16,3° Gels, (am 26. Januar 1870) 

 P.L. — 1605 =- + 0,245 mm bei + 18,5° Gels, (am 26. Januar 1870). 



Die Differenz beider Stäbe ist sonach bei den verschiedenen Temperaturen nahezu 

 dieselbe, sodass ihre Ausdehnungskoefficienten als gleich angenommen wurden zu 17,7 ju. 



IV. Die Vergleichung von A. W. Ghisholra, Standard Office, Westminster 

 wurde im Mai 1870 ausgeführt und lautet das Ergebniss im Original: 



7"^. Old Palace Yard, Westminster; May 6^^. 1870. 



Sir, No time has been lost in complying with your request to compare your metre 

 with our Standard Metre. 



It should be observed there is no legal Standard metre in this department. The 

 Standard Bar upon which our Scientifique Standard metre is laid down (designated as SS) 

 is of Baily's metal. 1 inch square like our Standard yard, and the measure of a metre, 

 with its various subdivisions, is marked with very fine lines upon gold studs. The coeflicient 

 of expansion of this bar has not been itself determined , but it is assumed to be the same 

 as other similar bars of this metal, namely 0,00000947 for 1° Fahrenheit. 



The length of the metre on SS was laid down from that of the Royal Society 

 (R.S.L.M.). Line Standard metre of platinum, constructed in pursuance of a Resolution of 

 the House of Gommons in 1818, and found by M. Arago to be less than the primary 

 Standard metre „des Archives" by 17,59 thousandth's of a millimetre, or 0,01759 mm. 



At the temperature of melting ice, it has been determined that 



SS = R.S.L.M + 0,02083 mm 



. • . SS =: metre des Archives -|- 0,00324 mm. 



Your Standard Metre (N) has been compared with SS by means of our mieroscopical 



apparatus, the mean of 12 readings ou each of the successive days been taken, 



Fahr. 

 1870. May 5 —mean— 54,5° — iV = ^S/S + 0,18302 mm (SS next observer) 



, 6 „ 54° —N= SS-h 0,18394 mm (N next observer) 



mean: iV = ÄÄ + 0,18348 mm 



and as: SS = + 0,00324 mm 



N"^ -\- 0,18672 mm. 



No reduction to 32° has been made, the coeflicient of expansion öf your bronce bar 

 being assumed to be similar to that of Baily's metal. It would foUow that your Standard Metre 

 is in excess of the „Metre des Archives" 0,18672 mm at the temperature of the melting ice. 



I am your obedient servant 

 A. W. Ghisholm. 

 To Prof. Dr. Neumayer. Warden of the Standard. 



