m 
FIFTH REPORT -1835. 
By which it appears that, from the mean of 56 comparisons, 
the centre yard of the Aberdeen scale is *001385 inch (or 
about of an inch) shorter than the centre yard of the Royal 
Astronomical Society’s scale, at the temperature of about 47° of 
Fahrenheit ’ s thermometer. 
I have also myself made 16 direct comparisons of the whole 
length of the same scales, namely 5 feet; and have obtained the 
following results, viz. 
1835. 
No. of 
Comp. 
Divisions of 
Micr. 
Temp. 
Observer. 
July 23. 
— 24. 
Mean = 
8 
8 
39-62 
39-24 
74*6 
72-7 
J Baily. 
16 
39-43 
73-6 
By which it appears that, from the mean of the 16 compari¬ 
sons, the whole measure of the 5 feet Aberdeen scale is *001971 
inch (or about of an inch) shorter than the whole 5 feet, of 
the Royal Astronomical Society’s scale, at the temperature of 
73°*6 of Fahrenheit. 
I beg to add that the Aberdeen scale is in very good condi¬ 
tion, and in excellent preservation : it appears to have been 
exceedingly well finished, and is by far the best of any that I 
have seen of Mr. Trough ton’s execution. And although the 
above results show a greater discordance from the correct mea¬ 
sures than is desirable, yet as perfect accordance is seldom or 
never attainable, no inconvenience can arise from this circum¬ 
stance, now the amount of the error is ascertained, and will 
consequently be known to those parties who may, at any future 
time, have occasion to make use of this scale. 
Independent of the value of these experiments in thus deter¬ 
mining the comparative length of the Aberdeen scale, they are 
important in a general point of view, in as much as, coupled 
with others that I have made with a similar object, they evi¬ 
dently show that the too prevalent notion 44 that standard scales, 
44 made from one and the same prototype agreeably to Mr. 
44 Troughton’s method, would accord with each other,” is not 
strictly correct. Indeed, it is now too evident (as I shall at 
some future time show more in detail) that a great number of 
minute, yet important, circumstances have hitherto been neg¬ 
lected in the formation of such scales ; and without an attention 
to which, they cannot be expected to accord with that degree 
of accuracy which the present state of science demands. 
