122 
alongside. Indead calm, few birds leave the ferry slips 
for the trip, and these labor heavily across in flapping pro- 
cession. 
From observation of land birds I have but one note of 
interest. It relates tothe repeatedly observed feat of a 
smallhawk. In this instance there isno advance in any 
direction. Like the humming-bird he stands poised, with- 
out visible support. at a point in space; but his out- 
spread wings and tail are as steadily held as if wired 
into place by the taxidermist. He points straight into 
the wind. If he utilizes its shifting ‘‘internal forces,” 
he draws upon them, with extraordinary expertness, for a 
constantly recompounded resultant, to be maintained 
equal, and vertically opposed, to the pull of gravity. With 
almost the suddenness of the humming-bird, he will dart 
from one fixed position to another, seemingly by expendi- 
ture of will power only. I believe that it is high winds 
alone that afford him this sport, or opportunity. And I have 
never seen him thus poised over level ground, but among 
hills, even with their summits, and from one to another, 
close in their lee, like the humming-bird, again, in a 
garden. On two occasions I have had a fine chance at 
this skilled aeronaut, from surveying stations on hill tops. 
I have been able to keep him for several minutes on the 
cross-hairs of my telescope. As with the sailing gull, there 
isthe same calm eye and the same quitk and delicate 
teetering of the wings; but the individual feathers, ex- 
cepting at their strongly up-bent tips, exhibit no blur of 
continuous motion. 
If my opinion in regard to such observations as these be 
correct, Mr. Amery’s assertion is disproved, and belongs 
toa stage of the investigation beyond which we have ad- 
vanced. WitiarRD D. JOHNSON. 
Le Droit Park, Washington, D. C. 
The Mining Building at Chicago. 
To what Mr. G. L. English so well says in Sczence of 
Feb. 16, in defence of the gallery exhibits against the 
slurs of the anonymous article in Sczence of Feb. 2, on 
“¢ The Columbian and the Centennial Expositions,” I wish 
to add a word for the ‘‘ground floor.” Much of the 
fault found by the writer of the article in question was 
deserved, but if he had looked for points of merit as well 
as of demerit he would readily have found them. The 
exhibit of New South Wales was wonderful for its extent, 
variety and completeness. It was a strictly economic 
display but not without scientific features as well. Every- 
thing in it was plainly numbered and labeled, and full 
descriptive catalogues with corresponding numbers were 
to be had freely on application. The Canadian Geological 
Survey made a very complete display of rocks, minerals 
and ores, in which specimens and groups were carefully 
arranged and plainly labeled, but the Canadians made an 
excellent showing at the Centennial and might therefore 
have been excluded from the comparison by this anony- 
mous correspondent. Pennsylvania, New York and 
Michigan made displays of their great specialties of pro- 
duction, which were well mounted and cased where 
necessary and were plainly labeled. New York’s geolog- 
ical obelisk was certainly of greater educational than 
technical value, while the needle of Pennsylvania anthracite 
coal representing the exact section of a single bed was 
instructive as well as impressive. North Carolina, New 
Jersey and Missouri aimed to have their exhibits of direct 
educational and scientific as well as economic value. 
New Jersey took especial pains to have her ores, minerals, 
clays and marls distinctly labeled and to put the labels 
where they could not be overlooked, while a complete 
SCIENCE. 
Vol. XXIII. No. 578 
series of the geological maps of the State adorned the 
walls of the space assigned to her. ‘The Missouri exhibit 
was labeled with the common as well as the scientific 
name and the chemical composition of each group of 
minerals or ores represented, in addition to the printed 
and written labels on each specimen. About 75 framed 
maps, charts, diagrams and photographs were displayed 
in this exhibit each of which bore an adequately descriptive 
label. The ‘‘great piles” of ore and metal here had a 
definite meaning, which was plainly stated on a large tabel 
prominently placed. I might go on and mention many 
points of excellence in other exhibits on the ground floor, 
without going into details as to the instructive array of 
mining, milling and quarrying machinery on exhibition, 
but I have said enough to show that there were more 
than ‘‘one or two” exceptions to this correspondent’s 
strictures. The general public seemsd, indeed, to care 
more for the Ada Rehan statue than it did for education 
in mining, mineralogy, or geology, but that is not the 
fault of the exhibitors who strove to instruct as well as to 
interest those who strayed into their spaces in the Mining 
Building, and I quite agree with Mr. English in thinking 
that the mining exhibit at Chicago far exceeded that at 
Philadelphia in every respect, though of course any one at 
all versed in the matter could detect many defects which 
might have been remedied. E. O. Hovey. 
New York, March tr. i 
Petrified Eyes. 
In Sczence of Feb. 2 Mr. Geo. G. Groff, under the title 
of ‘‘ Petrified Eyes,” calls attention to a statement in 
some popular school geology that ‘‘ huge saucer eyes,” of 
a thirty-foot monster, were so perfectly petrified that the 
“lenses have been split off and used as magnifiers.”’ 
About a hundred years ago some students of Paleon- 
tology, at Heidelberg, made to represent fossils, out of 
clay, spiders in their webs, snails with antennz perfectly 
preserved, a plump mouse, and other similar things, and 
left them where they could be found on class excursions. 
The professor described and pictured them in a book as 
remarkable fossils. On a latter excursion he found his 
name fossilized. He gradually realized that he had been 
hoaxed, and chagrin hastened his death. 
Ever since then it has been established that only 
chitinous, horny, or bony parts of an animal are petrified; 
soft parts are never petrified. They may leave impres- 
sions in a fine soft mud, as the examples of jelly-fish in 
the Solenhofen—Bavaria—stone so well show. The outlines 
of the body of worms, fish, reptiles, mammals, are pre- 
served by the shaping of the mud in which they were 
deposited—not by the membranes themselves being 
chemically replaced. This is true even of the tougher 
membranes of the body, as for instance the hide, and 
much more so with any part as delicate as the crystalline 
lense. The ease with which the lense is destroyed is 
shown by one of the three methods employed in treating 
cataract of the eye, where by means of needles the lense 
is broken up and is finally absorbed by the fluid in the 
anterior of the eyeball. 
Quarrymen seem to delight in finding ‘‘ fossil eyes,” as 
they name many things from the teeth of Gyrodus to 
quartz boulders. 
While the lense could not be petrified, the bony eye 
cavity, or the cavity formed by the sclerotic ring possessed 
by many fishes and reptiles (¢.g., Portheus, Ichthyosaurus) 
could be filled with gypsum, calcite, or quartz in such a 
manner as to furnish a plano-convex lense. 
A. R. Crook, 
Northwestern University, Evanston, Il). 
