432 
NATURE 
a ae 
| March 8, 1883 
to the subject of general laboratory and engineering work, 
Mr. Jamieson has made good use of the space at his 
disposal, and we have much pleasure in recommending 
his appendix as likely to prove exceedingly useful to 
electricians. 
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Mr. Stevenson’s Observations on the Increase of the 
Velocity of the Wind with the Altitude 
A HEAVY pressure of professional work has prevented me till 
now from noticing Mr, Archibald’s remarks on my paper on 
simultaneous observations of the wind at different elevations. 
I fear I have not been sufficiently explicit as to the object of 
my observations. All of them have reference strictly to the 
retarding influence of the friction caused by the earth’s surface, 
and are not so much of a meteorologic as an engineering character. 
This I thought would have been understood from my statement 
that I believed they were approximately correct ‘‘for practical 
purposes.” The formule are intended to be applicable only to 
heights within the limits of my observations, and the idea of 
applying them to the higher regions of the atmosphere, such as 
from 3800 to 23,000 feet above the earth, never for one moment 
crossed my mind, and I think the following facts observed by 
Mr. Glaisher in his balloon ascents prove the futility of attempt- 
ng to deduce from experiments made near the surface of the 
earth what the velocity of the wind may be at such great 
elevations. 
“Tn almost all the ascents the balloon was under the influence 
of currents of air in different directions.” ‘* The direction of 
the wind on the earth was sometimes that of the whole mass of 
air up to 20,000 feet, whilst at other times the direction changed 
within 500 feet of the earth. Sometimes directly opposite 
currents were met with at different heights in the same ascent, 
and three or four streams of air were encountered moving in 
different directions.” 
“On January 12, 1862, the balloon left Woolwich at 2h. 8m. 
p-m., and descended at Lakenheath, seventy miles distant, at 
4h. 19m. p.m. At Greenwich Observatory, by Robinson’s ane- 
mometer, during this time the motion of air was six miles only.” 
On June 26. 1863, ‘‘at go90 feet the sighing and moaning of 
the wind were heard, and Mr. Glaisher satisfied himself that this 
was due, not to the cordage of the balloon, but to opposing 
currents.’’ On the descent, ‘‘a fall of rain was passed through, 
and then Je/ow it a snow-storm, the flakes being entirely com- 
posed of spiculze of ice and innumerable snow crystals.” 
On July, 1862, the temperature of the air at starting was 59° 
Fahr., at 4000, 45°, at 10,000, 26°, at 13,000, 26°, at 15,500, 
31°, at 19,500, 42°, at 26,000, 16°. On descending, it was found 
to be 37°°8 at 10,000, while on the ascent at the same height, 
it was only 26°. 
Mr. Buchan states -(article ‘‘ Atmosphere,” ‘‘ Ency. Britt.,” 
gth edition): ‘* observations of the winds cannot be conducted, 
and the results discussed, on the supposition that the general 
movement of the winds felt on the earth’s surface is horizontal, 
it being evident that the circula’ion of the atmosphere is affected 
largely through systems of ascending and descending currents.” 
The observations in the higher regions of the atmosphere quoted 
by Mr. Archibald confirms this irregularity of the atmospheric 
currents ; as, for example, the velocity at an elevation of 1600 
feet is greater than at an elevation of 7200 feet, showing that no 
satisfactory results can be deduced from them, 
My observations on the 50-feet pole are onlyjapplicable to 
‘*small heights” above the ground, and they have proved the 
absolute necessity of all anemometers being placed at one uni- 
form height above the ground, and are mainly useful in enabling 
us to reduce anemometric observations obtained by instruments 
at different heights to the same standard level—a matter which, 
as a meteorologist, I deem of great importance. 
I believe that the formula for small heights will be useful, 
because I consider it applicable to such engineering works, for 
example, as the Tay and Forth Bridges. 
As regards the other observations with pressure anemometers 
at comparatively great heights, the highest observed being 1600 
feet at the Pentland Hills, the simple formule which I pro- 
posed were made only to cover the observations which I actually 
obtained, and they do agree nearly with these results. As to 
the assertion that I supposed that the force of the wind ought 
to vary as its velocity, the contrary is the fact, as Mr. Archibald 
might have seen by my statements that the only hypothesis on 
which 1 could account for the paradoxical re-ult of the same 
formula being practically applicable both to force and yelo- 
city was the decreased density of the air as we ascend. I 
Observations on Velocity at Arthur's Seat 
| = oe 5 
Velocities computed for lower station 
Velocity = 
Velocity 
recorded at | By Mr. | y Mr. By Mr. recorded at 
high elevation. Stevenson’s | Stevenson's Archibald’s | low elevation. 
| rst formula. | 2nd formula. formula. 
5 feet above | z — h\| 9—VA | 5-1 b/d | 550 feet abo 
ees ea firs Paid Fs v lea 
I | 
| 
885 703 | 592 766 720 
1,698 | 1,430 1,205 1,558 1,364 
23620 ©) || +2}2064 9), = 1859 2,405 2,133 
3,416 | 2,876 2,424 3,132 2,718 
4,328 3,646 3,071 3,973 3,465 
5.575 4,697 3,957 5,117 4,592 
6,763 5,698 4,800 6,208 5,640 
8,035 6,765 5,702 7,376 6,782 
9,368 7,893 | 6,648 8,600 7,862 
10,820 9,115 | 7,679 9,933 8,765 
12,410 10,455 8,807 11,392 9,789 
13,709 11,542 9.722 12,576 10,639 
15,058 12,687 10,686 13,833 11,680 
+ 13 79,713 67,152 | 86,869 76, 149 
Mean results) 6,132 5,165 6,682 5,857 
Calculations for lower station 
Height of =. By Mr. By Mr. By Mr. 
eariens s OREN EUE Sieeausents Sieeensaes Archibald’s 
Jahores At higher) At lower | ist formula. | 2nd formula. formula. 
in feet. station. | station. } FA Fh 4 ar 
=F fe = ae A 
ey ec etait Vv i 
nw || FAAS | — — = 
1500 — | 57250 | 5424 | 5°246 5-491 
TROON s|)05542) | a | = =F = 
gI5 —_ 5000 | 6671 | 5°208 7°516 
438 5077 ae = | — — 
371 —_ | 4259 4675 4°301 4873 
37 W455 alee ln es aS 
276 — |4181 | 3945 | 37405 4247 
Average for 5 | 5 | : ; 
lower stations | | 4 oe | 5179 | 4°540 5°53? 
am not prepared to admit that the velocity at 100 feet above 
the sea will, as Mr. Archibald supposes, be much greater than 
at sea-level, for my simultaneous observations of wind pass- 
ing over the sea, over sand and over grass (Min. Cir. Eng.) 
render it doubtful. If for example a wind passes over the 
surface of the sea with a given velocity, which will depend 
to a certain extent on the comparatively small amount of friction 
due to passing over water, that velocity will be at once reduced 
when the current meets the shore and begins to pass over the 
more retarding surface of solid land. At a height of 100 feet 
above sea-level, it may not therefore have attained the initial 
velocity which it had at sea. But as to the whole subject, which 
