all 
XVi 
of the wind such as occurs diurnally in land- and sea-breezes 
near the coast. I am now able, by the kindness of. Major 
Pendlebury, to bring forward a striking instance in which 
the cause and effect were observed. 
Daily Migrations against a Land- and Sea-breeze by Pyrameis 
cardui, by W. le M. Pendlebury. 
* Immediately after the second battle of Gaza, April 17-19, 
1917, my observation-post was placed on the inner side of a 
ledge of cliff on the edge of cultivated land that lay between 
the British trenches round Gaza and the Turkish lines. I 
had been in the observation-post for about ten days when 
one morning at about 9.30 a.m. I noticed a cloud of P. cardui 
passing over me and going down towards the cultivation which 
was then green barley, with many flowers in it. The flight 
continued for about three-quarters of an hour. I was struck 
by their persistent appearance, and on the second day made 
a point of being there on the look-out. Almost at the same 
time as on the previous day they appeared again, flying in the 
same direction—N.W.—and in scattered bunches of 5-12 
together. They also on this day continued to fly for about an 
hour, but towards the end of the time came singly or in twes 
and threes. 
“Tn the late afternoon—5.30 p.m.—TI was surprised to see 
the same species returning from the direction in which they 
had gone in the morning. They were not, however, nearly 
so numerous. My observations lasted for about ten days, 
and towards the end of that time it would be difficult to call 
the morning flight a migration, as the numbers were greatly 
reduced. In the early part of the time along ten yards of 
cliff the numbers averaged 40 a minute, which dwindled down 
to 10a minute. After the first three or four days the numbers 
were about 20 a minute during the rush time, and the latter 
half of the ten days the average was 10 a minute. After that 
there were a few flying over casually but always in the same 
direction. The evening migrations towards the end of the 
time became very reduced. 
“The sea-breeze from the N.W. usually began to blow 
about 9 a.m, and left off about 5 p.m., and then the land- 
