LIEUT. -COL. A. R. CLARKE ON STANDARDS OE LENGTH. 
449 
The Klafter. 
Two copies of the Vienna Klafter have been compared at Southampton, viz. the 
Pulkowa copy and the Milan copy. In order to effect the measurement of the klafter, 
it was most convenient to construct, in the first instance, a bar of the length of half a 
klafter, to determine its length by comparison with the standard yard and standard foot, 
and then to compare the klafters with two lengths of this bar. 
The half klafter was constructed by Messrs. Teougiiton and Sims ; it is of Swedish 
iron 38*3 inches in length, TO in breadth, and 0*475 inch in depth. On its upper surface 
it bears four raised disks, marked a , b, c, d ; the distance a & = 1*33 inch, b c— 4*00 inches, 
and b f^ = 36 inches; thus the distance between the transverse lines on a and d, marking 
the total length of the half klafter, is 37*33 inches approximately. The necessity for 
the line c arises from the circumstance that the small space a b could not be compared 
with a corresponding space on the standard foot, as two micrometer-microscopes cannot 
be fitted up at so small a distance apart ; consequently a b is determined as the difference 
between the spaces ac=5*33 inches and bc= 4*00, which two spaces were compared 
with corresponding spaces on the standard foot. We shall designate this bar by the 
symbol Ki. 
For convenience, and to save reference to the former paper, it maybe well to explain 
that the standard foot has on its upper surface thirteen division-lines marked a , b , c, d, 
e,f , g , h, k, l, m, n, p, marking the twelve inches. The first inch ( a b) is subdivided into 
tenths by lines marked (from a towards b) 1, 2, 3, 4, 5, 6, 7, 8, 9. The tenths [2 . 3] 
and [6.7] are subdivided again into tenths. In the former of these spaces falls the 
toise-line r, and in the second the metre-line [h. The line by which the length of the 
half klafter is determined also falls in [6.7]; it is the seventh line from 6 towards 7, 
or the third line from 7 towards 6. The error of this line with reference to the lines 
6 and 7 is, the unit being the one millionth of a yard, 
^=-4*29+0*085; 
that is to say, if [6 . k~\ be the distance from the line 6 to the line k, 
[6.*l=A[6.7]+*». 
The space \a c\ of the half klafter was compared with the space \k g~\ on the standard 
foot. We therefore require to have the probable error of \_kg~]. Now [k g~\ = [a g ~\ — [a k~] ; 
and expressed in terms of the errors of the other lines the value of \Jc g] is 
r7 533 T 3x 6 h lx 1 6jx b 533x g 
9 \ = foo J T(7 To — too ' 600 ’ 
where x 6 x 7 are the errors of the lines 6 . 7 with respect to the lines a b, and x b x s the 
errors of the lines b g with respect to the lines ap. Also I=i 1 2 of the standard foot F, 
From this expression we can at once determine the probable error of \k g~\ ; we shall 
not enter into the details of the calculation, but simply give the result, namely, 
1+1-40+0*108. 
