Marcu 14, 1884. | 
Stones placed in pine-trees by birds. 
About seventy-five miles south of the United States 
boundary, near this place, at an elevation of six thou- 
sand feet, is a stretch of table-lands covered with large 
pines (Pinus Jeffreysi?), broken by many ridges of 
giant granite bowlders, decomposing sufficiently to 
add materially to the soil. Broad, grassy meadows 
furnish food for cattle and deer. 
My father and myself, inriding through this forest 
in July, 1883, noticed several pines with the bark 
bored into at varying distances from the base of the 
tree to the branches; and in about one-third of the 
holes were the acorns of the here common Quercus 
Emoryi, very tightly fitted, the holes containing the 
acorns apparently newly made. The remaining holes 
were weather-beaten ; and in them were equally tightly 
fitted bits of the granite gravel, of size corresponding 
with the acorns in the otherholes. In the Cuyama- 
ca Mountains, of this county, a gentleman observed 
Colaptes auratus visit pines that contained similarly 
disposed acorns. The woodpecker tapped the acorns, 
breaking one now and then; the broken shells show- 
ing plain traces of having contained a worm, while the 
other acorns contained sound kernels. But what ob- 
ject could the birds have in substituting stones as 
shown above? Possibly they served as hiding-places 
for many insects which would otherwise have secured 
places inaccessible to the birds. Cs) kh: ORCUTT. 
San Diego, Cal., Feb. 16. 
How a spider sometimes lifts heavy objects 
to its nest. 
Last summer, while at Lynchburg, Va., [observed 
a spider— probably an Epeira— spinning a thread 
down from the upper section of a large fountain on 
the lawn of the Arlington hotel. He wassome eight 
feet from the surface. I watched him descend to the 
water, where he captured a beetle that had unfor- 
tunately fallen into the large basin. The beetle must 
have been an inch long. Our Epeira made a turn 
of his line around his captive, and ascended all the 
way to his nest; immediately descending, he threw 
another loop around his prey, and again ascended 
to his nest, continuing this process for full ten min- 
utes: to my surprise, while the spider was at his web, 
apparently overhauling and tightening the several 
threads that he had spun to and from the beetle, it 
left the water, and, evidently by elastic contraction of 
the threads, ascended full an inch from the surface. 
The spider spun down another lasso, and threw it 
round his victim, then retired and was busy with 
his lines, when the beetle again moved upwards. 
These operations were repeated, until, at the end of 
forty-five minutes, he had snugly secured his prey in 
his nest, at a distance of at least eight feet from the 
water, by this curious and interesting method. 
Cambridge, March 3. E. P. LARKIN. 
The use of the method of limits in mathemati- 
cal teaching. 
I notice in a recent number of Science a proposal 
to discuss the different methods of teaching the ele- 
ments of the infinitesimal calculus, and, in connec- 
tion with this, an allusion to Professors Rice and 
Johnson’s ‘ New method of rates.’ 
I trust it is not out of place to suggest that the 
method in question seems to me very like the method 
given in Maclaurin’s ‘ Fluxions,’ which the author 
attributes, at least partially, to Newton; and that the 
present very general use of the method of limits is 
probably a case of ‘the survival of the fittest:’ forI 
have found in my experience as a teacher that those 
SCIENCE. 
305 
who are either too young or too slow to acquire at 
once the deeper conceptions of mathematics are often 
capable of doing very good work when the demon- 
strations are adapted to their comprehension. 
The method of limits seems to me that which must 
be used with a class, if it is desired to give a sure 
foundation to as many as possible; the method of 
rates or fluxions requires rather more preparation of 
mind; and the infinitesimal method is best adapted 
to those who have mathematical genius. 
The average engineer or architect is a person whose 
natural bent is towards construction and the use of 
tools. Such a person will, in all probability, require 
the infinitesimal calculus as a tool rather than as a 
recreation or a profession, and should therefore be 
trained by a slow and certain process—like the 
method of limits—in order that his real abilities 
may not be disguised by any slowness of comprehen- 
sion in a matter which he can by patience acquire. 
The weakness of mathematics as a general study 
in our institutions lies in the rapidity with which the 
successive steps are passed over; so that the slower 
pupils are left behind, and become discouraged. Old 
country schools do more solid work in average cases. 
TRUMAN HENRY SAFFORD. 
Williams college, March 1. 
THE INTERNATIONAL BUREAU OF 
WEIGHTS AND MEASURES.! 
THe annual report of operations for 1883 
has just been received. It shows a steady ad- 
vance towards the completion of the interna- 
tional standards. All the principal instruments 
and apparatus have now been procured, and are 
in position. The comparateur géodésique, for 
which a contract was made with the Société 
Génevoise in 1882, was to have been delivered 
by August of last year. Various events con- 
spired to delay its complete delivery; but at 
the close of the report the entire apparatus was 
on its way, and was to be set up in the early 
part of January. All necessary masonry work 
was done in the spring of 1883. 
Changes have been made in the method of 
heating the room of the Brunner comparator. 
Hitherto it has been done by regulating the 
temperature of water held between the double 
zinc walls in which the room is enclosed. It 
has been found, however, that, in addition to 
the difficulty and expense of maintaining a con- 
stant temperature of the water day and night, 
trouble was experienced from frequent leaks 
in the zine walls, necessitating repairs, and 
stopping the observations: consequently the 
maintenance of temperature by the use of hot 
water has been discontinued ; and for it has 
been substituted hot air, which so far has 
proved satisfactory, and which, it is hoped, 
will solve the problem of heating. 
1 Comité international des poids et mesures. Septiéme rap- 
port aux gouvernements signataires de la convention du métre 
sur l’exercice de 1883. Paris, 1884. 54p. 4°. See also Science, 
No. 16 
