70b* 



PROF. C. P. SMYTH ON THE GREAT PYRAMID. 



The whole of the above operations for obtaining the length of the ell were performed, indepen- 

 dently, by Mr Chany, an officer of the Exchequer accustomed to such work, and an excellent 

 manipulator, and by myself; every adjustment was disturbed between the two determinations. 

 Neither in the line drawn on the ell, nor on that drawn on the piece of brass, did Mr Chany and I 

 differ perceptibly, a hand magnifier being used for the examination. The thermometer in the room 

 stood steadily at 69° throughout ; but no attempt was made to obtain the true temperature of the 

 ell, comparator, &c., which were necessarily handled a good deal. 



My own conviction is, that this comparison of Queen Elizabeth's ell with the Exchequer standard, 

 cannot differ so much as (0-005 in.) five thousandth of an inch from the truth. 



Queen Elizabeth's ell is a half-inch square prism, made of some red metal, very dark generally 

 from oxidation, but showing a colour like soft gun-metal in places. It is very roughly made, 

 no surface approaching a plane, and no corner a right angle. The two extremities are stamped 



thus 



The ends, defining the measure, are tolerably 



smooth, and irregularly convex. The stamped side has coarse graduation on it. The divisions 

 (filed apparently) are at the following distances from one end, viz., 2-75, 5 65, 11-30, and 22-50 

 inches. Intended, as these evidently are, as half, quarter, &c. of the ell, their errors may perhaps 

 afford some criterion of the dependence to be placed on the standard as a whole. 



Experiment 5, at Messrs Troughton and Simms's. 



August 4, 1864. 



The piece of brass was compared with 9 inches of Messrs Troughton and Simms's brass scale, by 

 means of their comparing apparatus furnished with two micrometer microscopes. Independent 

 observations were made by Mr William Simms (W. S.) and myself (A. S.), as follows : — 



W. S. 

 Rev. Div. 



A. S. 

 Kev. Div. 



62-0 



Between one pair of parallel longitudinal "I „ 

 lines on the piece of brass, ... J 



Between the other pair, \ ' i 



Thermometer, 71 '5. 



59-5' 



59 7 



Messrs Troughton and Simms's brass scale is taken as exceeding the Exchequer standard (O'OOl) 

 one thousandth of an inch per yard. 



The value of one division of the micrometer is (000004) four hundred thousandths of an incli. 

 Each revolution of the micrometer contains (100) one hundred divisions. 



I deduce from the above experiments, as an approximate result, xuicorrected for temperature, 

 that Queen Elizabeth's ell = Exchequer yard + 9*0386 inches. 



(Signed) 



A. Strange. 



