6 NATURE 
[May 7, 1885 
some indication of their presence. This year I ascertained the 
positions of several of these showers with great care. The 
number of meteors from them averaged from 3 to 5 only, but the 
paths intersect nearly at a point in the individual cases, so that 
the centres are entitled to the same value as positions resulting 
from a large number of tracks. I give the best of these co-Lyrid 
showe-s, and the nearest confirmations from previous observa- 
tions :— 
Observed Previous 
1885 Observations Authority 
April 78 ... 181 + 35) oe 184 + 35 .» March 31-April 12, D.S., 1872. 
10 .«. 236 + 62 240 + 55 ... April 14, Schiaparelli and Zezioli. 
20 61226 + 4r ... 223 + 40... March 12-April 30, Greg and Herschel. 
296+ o 294 + o... April 16-19, 1877, D 
.. April 25-24, Heis. 
.. April 16-19, 1877, D. 
.. April-May, Corder. 
.» April 13-May 11, Heis. 
5 .. April 16-19, 1877, D. 
The two radiants observed here in 1877 and 1885, with mean 
position at 295° + 0° and 298°°5 + 24°°5, are very interesting. 
The former, just preceding » Aquilz on the equator, supplies 
meteors of very great velocity, the latter in Vulpecula gives 
swift, streak-leaving meteors. This pair of showers, directed 
from points near the apex of the earth’s way, are now, I believe, 
very exactly determined in regard to their centres of radiation. 
That they have hitherto evaded frequent detection is not sur- 
prising, as they only become well visible in the morning hours. 
It will be useful to watch for these special streams during future 
exhibitions of the Lyrids, as well as to note the several other 
interesting features closely associated with this well-known 
display. W. F. DENNING 
Chinese Insect Wax 
THE beetle alluded to in connection with this subject in the 
last number of NATURE (vol. xxxi, p. 615) is a probably unde- 
scribed species of Brachylarsus, a genus of the family Azzthrz- 
bide, allied to the Curculiontde. Through the courtesy of the 
authorities at Kew I have had specimens before me. The idea 
that it acts as a sort of midwife to assist at the birth of infant 
Coccide is quite erroneous. The genus Brachytursus is a true 
parasite on Coccus, and its habits, in this connection, in Europe, 
have long been known. It is of course interesting to find 
** unity of habit” prevailing in the case of Coccus Pé-la, even to 
its parasite ; but with regard to the latter there is nothing new ; 
some points in the general economy of the wax insect, in the 
notes published, are of far greater importance. 
Lewisham, May 1 R. McLACHLAN 
The New Bird in Natal 
THERE can be little doubt from the description given by Mr. 
Turnbull in your issue of April 16 (p. 554) that the bird lately 
obtained by him in Natal is the Standard-winged Nightjar, 
Cosmetornis (seu Macrodipteryx) vexillarius, Gould. It has not 
been met with in Cape Colony, which accounts for Mr. Turn- 
bull’s inability to find mention of it in Layard’s ‘* Birds of South 
Africa ;” but in Mr. Sharpe’s new edition of Layard’s work 
(which Mr. Turnbull would do well to procure) he will find an 
account of this bird given at p. 89. It appears to have a wide 
geographical range, being found both on the west and east coasts 
of Africa ; in Angola and Damaraland, in Natal, on the Zambesi 
(where 300 miles up the river Dr. Kirk found it quite common), 
in the islands of Bourbon and Madagascar, along the Red Sea 
shore, and on the island of Socotra. With this extended range 
it is somewhat remarkable that it has not yet been met with in 
Cape Colony. According to the observations of Dr. Kirk the 
singular prolongations of the primaries are peculiar to the males, 
and a seasonal peculiarity observed only during the months from 
October until January. The habits of this bird, like those of 
other nightjars, are crepuscular. An excellent coloured figure 
of the male is given in Gould’s ‘* Icones Avium.” 
J. E. HartTiInc 
Wild Bees 
A FEW words respecting a colony of wild bees (a spesies of 
Andrena) which I have just discovered in our garden, may 
interest your entomological readers. A day or two ago, on 
walking beside a low-turfed mound which supports two trees on 
one of our towns, I noticed that the grassy surface on the south 
—therefore the sunny—side was covered with little hillocks of 
earth, such as ants throw up after rain. On examination each 
little heap showed the circular hole which denotes a bee’s nest, 
and the bees themselves were seen in many places going in and 
out. Some holes were level with the ground, but most had the 
tiny mound of soil cast up in the process of excavation. The 
peculiarity of the case seems to me to lie in the great number of 
nests forming a complete colony. It is difficult to count them, 
but there cannot be less than eighty or ninety in an area— 
roughly calculated—of about sixty square feet. Have any of 
your readers noticed a similar city of these busy people? and 
can any one supply the specific name ? E. BROWN 
Further Barton, Cirencester, May 2 
ON M. WOLF’S MODIFICATION OF FOUC- 
AULT'S APPARATUS FOR 1HE MEASURE- 
MENT OF THE VELOCITY OF LIGHT 
O one who has the true interests of scientific accu- 
racy at heart can fail to welcome any innovation 
whereby the elements of a research may be varied, for 
thereby the ever-lurking constant error is most readily 
eliminated. It seems, therefore, that this in itself is 
sufficient reason for the interesting paper communicated 
by M. Wolf to the Académie des Sciences (Comptes 
Rendus, 9 Février), describing a very ingenious arrange- 
ment of Foucault’s experiment, and that there was no 
occasion for disparaging other work in order to justify 
its publication. It is to be hoped that this was done 
rather through inadvertence than design, but I feel called 
upon to correct some of the misapprehensions under 
which the author labours, and particularly those concern- 
ing the appearance and distinctions of the image of the 
slit in my work on the velocity of light. 
M. Wolf remarks that, under the conditions which I 
selected, this image, even under the most favourable cir- 
cumstances, must be bordered with very large diffraction 
fringes, which the atmospheric disturbances transform 
into a badly-defined “‘ ¢ache /umineuse.” In reply to this, 
though I grant that the fringes owghz to be present, yet I 
can affirm as a matter of fact that they were not to be 
seen. Possibly M. Wolf and others may have been 
somewhat misled by a drawing of the appearance of the 
image given in my work (p. 124, Astr. Papers, Americar 
Ephemeris,and Nautical Almanac, vol. i. Part 3) where the 
image proper, which is quite clear, is surrounded by a 
luminous haze, from which, however, it is very easily 
distinguished. 
I hardly think that if M. Wolf had given the “ specimen 
observations” (p. 133 of my work) due consideration, he 
would have characterised as a “‘¢ache Jumineuse” an 
image whose position was measured with the following 
results (each result is the mean of ten observations made 
by one observer, and recorded without divulging the result 
by another) :— 
No. 1 112‘8or mm. 07020 mm. 
7 2 ESTs) as s-. (OFODON is 
Hs} 112°769 ,, orolo ,, 
» 4 112772 ,, - 0°007 5; 
ae) 112°779 35 +++ 07000 ;, 
Average difference from mean = 00286 ,, 
These are measurements of the deflected image, so that 
the differences are not merely errors of linear measure- 
ment, but include errors in the estimate of the speed of 
the revolving mirror. 
Now, M. Wolf, in his most sanguine statement, does 
not hope for a greater degree of accuracy than one part 
in 3500 in this particular measurement, whereas the 
above results are on the average closer than one part in 
10,000. 
But let us examine the data on which he bases this 
