182 Transactions of the Boyal Microseojpical Society, 
corresponded with my view of them through a good telescope. 
Another individual distinguished two children ascending the sunny 
side of a hill, and the colour of their jackets, at a distance exceeding 
half a mile (also verified with a good opera - glass). The same 
person could see bullet marks at 500 yards. Another fact was very 
surprising. I watched from the Eamsgate sands, for a long time, 
in 1844, a balloon (which had gone off towards Holland) with a 
small opera-glass magnifying about 2^ times. Long after it 
ceased to be visible to me with this aid, the sailors lounging about 
kept watching it still, and several saw it distinctly with the naked 
eye. 
Another circumstance is worthy of note. In some persons 
striations or rows of beads can only be seen when presented to the 
eye at a certain angle. I recollect every one of a party of gentle- 
men at my house, except one, saw distinctly a microscopic field of 
this nature. I then said to him jocularly, " Turn your head on one 
side," when to his surprise the definition became quite distinct. I 
have often observed highly skilled opticians perform the very same 
gyrations. 
Mr. Broun,.r.RS., says* (by error Colonel Woodward spells it 
Brown) : A dark brown hair '0026 inch wide, 2 '5 inches long, was 
fixed by dots of transparent gum-arabic to the window-pane, and 
was seen by a young eye against a N.W. sky at 36 feet distance ; 
the diameter of the hair subtended an angle of 1"'24 (IJ seconds 
of arc). Mr. Broun required it to be placed at 30 feet distance, and 
this would give a visual angle of l"-54, a quarter of a second 
greater. 
It may be interesting to the reader to know that a white disk 
of paper one inch in diameter forms a visual angle of 
1" at 206265 inches distance, or 5730 yards. 
2" at 103132 „ „ 2865 „ 
3" at 68755 „ „ 1910 „ 
6" at 34378 „ „ 955 „ 
60" at 3438 „ „ 95 „ 
Now a visual angle of two seconds is equivalent to 
A line to-ttts diameter, distant 1 inch. 
Aline „ „ „ 10 inches. 
In agreement with this, Mr. Broun states a young eye, he 
finds, can actually see lines on glass to^^o^ i^ch wide, long. 
If therefore the 10,000th of an inch can be seen with the 
naked eye, without a lens, it ought to follow that the 100,000th of 
an inch ought to be seen by the same acute eye, with a power 
magnifying ten times. 
Now Nobert's lines 112,000 to the inch, probably have inter- 
* ' Proceedings Royal Soc' p. 523, vol. xxiii. 
