192 
NATURE 
[APRIL 25, 1912 
ness has its usual effect of facilitating the propaga- 
tion of electric waves over great distances, but that 
there are portions of time during the period of greatest | 
‘and the air saturated. At 885 metres, however, the 
‘temperature was 32’9° F., the’ wind direction S.E., 
darkness at the receiving station when propagation 
is hindered. This minimum is not an accident, and 
was, in fact, not unexpected by me. It can be ex- 
plained in some measure by a hypothesis which I 
have embodied in a paper and submitted to a learned 
society; but until the paper is published I feel pre- 
cluded from discussing the phenomenon, and am 
writing to you merely to put the results of the observa- 
tions on record. 
I may add that Mr. Lempfert, of the Meteorological 
Office, has kindly informed me that there was not 
any trace of thunderstorm during the eclipse shown 
on the Daily Weather Reports of April 17 and 18. 
The distribution of pressure was not favourable for 
thunderstorms over the continent of Europe, though 
electric disturbances may have occurred in the low- 
pressure systems over the Spanish peninsula and the 
north of Norway. W. H. Ecctes. 
37 Chelsea Gardens, S.W., April 10. 
Glazed Frost. 
Jupcine from the letters recently published under 
this heading (Nature, pp. 414, 447, 484, 516, and 
550), the phenomena known in New England. as ‘ice 
storms ”’ are of rare occurrence in Old England. They 
are of frequent occurrence along the Atlantic coast 
of North America, and the conditions which produce 
them are well understood. 
In W. M. Davis’s ‘‘Elementary Meteorology ” 
(1893), p- 294, they are described as ‘follows :—‘t Re- 
gions of strongly variable temperatures are subject 
to occasional. winter storms in which the precipitation 
occurs. as rain, but freezes’ as soon as it touches 
any solid body, such as the branches of trees, or tele- 
graph wires, or the ground. This happens when 
the ground and the lower air- have been made exces- | 
sively cold during a spell of clear anticyclonic weather, 
when a moist upper. current: in advance of an ap- 
proaching cyclone brings clouds and rain. Serious 
damage is caused by breaking down over-weighted 
wires and branches at such times. Wires may be 
increased -in’ weight’ ten to twentyfold, and twigs 
even more than a hundredfold.”’ 
Hann describes the | 
phenomenon under the term ‘‘Glatteis”’ in his ‘‘ Lehr- | 
buch der Meteorologie "’ (1906), p. 190. 
In a recent study of New England ice storms made 
under the direction of Prof. A. Lawrence Rotch by 
Mr. Charles F. Brooks in a research course in Har- 
vard University, he found that twelve such storms 
occurred each year in the average for the period 1886 
to 1911, inclusive. For the various months the fre- 
quency of occurrence was in the following order : 
January, February, March, December, November, 
and April. He concluded that the essential and ever- 
present conditions accompanying ice storms were: (a) 
rain falling; (b) when the temperature of the lower 
air was below freezing; and (c) with an inversion 
stratum aloft in which the temperature was above 
freezing. He found that the raindrops coming from 
the relatively warm stratum aloft are cooled below | 
their freezing point as they pass through the colder 
stratum beneath, but are not solidified before reach- 
ing the ground or exposed objects, on which they 
form an ice sheet. On December 13, 1895, rain con- 
tinued to fall when the temperature of the lower air 
was but 9° F. 
Data obtained in kite flights during ice storms at 
Blue Hill Observatory verify the presence of this 
inversion stratum aloft. On February 9, 1005 (see 
Annals of the Astronomical Observatory of Harvard 
College, vol. Iviii., part iii., p. 168), the temperature 
NO. 2217, VOL. 89| 
decreased with height from 293° F. at the observa- 
tory, 195 metres above sea-level, to 276° F. at 702 
metres, the wind being uniformly E.S.E. in direction, 
and the humidity 100 per cent. The base of the 
| relatively warm stratum from which the moisture 
came in the form of raindrops was apparently between 
the last two heights quoted. The drops were under- 
cooled as they descended through the colder stratum 
| beneath, but did not change to ice until striking the 
ground. A somewhat similar condition was observed 
in the last international kite flight, that of March 7 
last. On that occasion the auxiliary kites added to 
lift the line became so heavily coated with ice that 
they pulled the leading kite down instead of aiding 
its ascent, thereby rendering the maximum height 
reached during the flight ‘considerably lower than 
usual. On that occasion the air was practically iso- 
thermal from the summit of Blue Hill to 625 metres 
| above sea-level, the temperature being about 30°8° F-. 
Above the latter level, however, the temperature 
increased steadily with height, and was 368° F. at 
874 metres, the maximum height reached by the 
leading kite. Rain falling from this relatively warm 
stratum was undercooled by its passage through the 
colder air below, and changed to ice upon reaching 
solid objects. 
Inthe vicinity of the observatory, after the occur- 
rence of recent ice storms, it is not uncommon for 
the ice to accumulate to a depth of an inch on all 
exposed objects, and on one occasion, February 14-16, 
1909, ice formed to a thickness of three inches, and 
did not disappear until February 20. During such 
storms we are able to keep the anemometer in opera~ 
tion only by frequently dashing hot water over the 
revolving cups and the other exposed parts. 
Blue Hill Observatory, ANDREW H. PatMeEr. 
Hyde Park, Mass., April 2. 
f Animal Intelligence. 
Tue following incident may be of interest to 
readers of Nature. 
We have a black retriever dog, very well trained. 
She is kept chained in a kennel in the yard, to which 
a number of fowls have access. During the last few 
days a black hen nearly every day lays an egg in the 
kennel, the dog meanwhile sitting outside. Unless 
someone takes the egg out directly afterwards, the 
dog takes possession of it and eats it. 
This curious proceeding raises the question whether 
the hen lays the egg in the kennel for the dog’s 
benefit, and whether the dog for her own advantage 
allows the hen to enter the kennel without molesta- 
tion. M. N. W. 
Frankland, St. Leonards, near Tring, April 19. 
THE ECLIPSE OF THE SUN ON APRIE ty. 
Te solar eclipse which occurred on April 17 
appears to have been observed under ideal 
conditions all along the available track, and the 
question as to whether a total eclipse would occur 
is settled in the affirmative, for a totality of one- 
half to one second was witnessed in Portugal 
near Ovar. 
No astronomical phenomenon of recent years 
appears to have attracted more general popular 
attention. Even the Lords Justices temporarily 
adjourned their sittings at the Law Courts in order 
to witness the unusual event. 
A large number of well-known astronomers 
