SCIENCE. 
i5i 
would be sufficient to enable one to see a molecule of al- 
bumen, or if its power could be increased one hundred 
and seven times it would enable one to see a molecule of 
alum. 
Now Helmholtz has pointed out the probability that inter- 
ference will limit the visibility of small objects ; but sup- 
pose that there should be no difficulty from that source, 
there are two other conditions which will absolutely 
prevent us from ever seeing the molecule. 
1st. Their motions. A free gaseous molecule of hydrogen 
at the temperature of 0 °C., and a pressure of 760 mm. 
mercury, has a free path about ruooir mm. in length, its 
velocity in this free path being 1S60 m. per second or more 
than a mile, while its direction of movement is changed 
millions of times per second. Inasmuch as only a glimpse of 
an object moving no faster than one millimeter per second 
can be had, for the movements are magnified as well as the 
object itself, it will be at once seen that a free gaseous 
molecule can never be seen, not even glimpsed. But sup- 
pose such a molecule could be caught and held in the field 
so it should have no free path. It still has a vibratory 
motion which constitutes its temperature. The vibratory 
movement is measured by the number of undulations it sets 
up in the ether per second, and will average five thousand 
millions of millions, a motion which would make the space 
occupied by the molecule visibly transparent, that is it 
could not be seen. This is true for liquids and solids. 
Mr. D.N. Hodges finds the path of a molecule of water at 
its surface to be .0000024 mm., and though it is still much 
less in a solid it must still be much too great for observation. 
2d. They are transparent. The rays of the sun stream 
through the atmosphere, and the latter is not perceptibly 
heated by them as it would be if absorption took place in 
it. The air is heated by conduction, contact with the 
earth, which has absorbed and transformed the energy of 
the rays. When selective absorption takes place the num- 
ber of rays absorbed is small when compared with the 
whole number presented, so that practically the separate 
molecules would be too transparent to be seen, though 
their magnitude and motions were not absolute hindrances. 
ON THE AURORA AND ZODIACAL LIGHT OF 
MAY 2, 1877. 
By Henry C. Lewis. 
A simultaneous appearance of an aurora and the zodi- 
acal light appeared on this evening, and a comparison be- 
tween them is here given. The various changes of the au- 
rora are given in detail. A remarkable feature was the 
formation of a bright streamer which maintained its posi- 
tion relative to the earth for nearly an hour. Meanwhile, 
the Zodiacal Cone, which was bright early in the evening 
had moved past the streamer and passed below the hori- 
zon. The streamer had remained, like the great pointer 
fixed to the earth, and marking its motion, while the 
heavens revolved past it. This fact was conclusive evi- 
dence of the terrestrial character of the aurora and of the 
cosmical character of the zodiacal light. Another fact 
leading to the same conclusion was the character of their 
spectra. That of the zodiacal light was continuous, and 
that of the aurora was a line-spectrum — the former is such 
as would be given by sunlight reflected from matter in 
space; the latter would he given by an electric discharge 
through a gas. 
OBSERVATIONS ON BRACHIOPODS. 
By Prof. Edw. S. Morse. 
Mr. Morse gave the anatomical details of some Brachio- 
pods he had studied in Japan, and described the existence 
of a curious parasitic worm in a large species of Lingula. 
He also gave further facts regarding the so-called hearts of 
certain brachiopods, and expressed his belief that they were 
glands of some kind connected with the reproductive 
organs. 
THE KAMES OR ESKARS OF MAINE. 
By Geo. H. Stone, Kent's Hill, Me. 
This paper is accompanied by a map showing the courses 
of the larger Kame-systems of Maine. Omitting short, 
isolated ridges of gravel, the map shows thirty distinct 
systems of Kame gravels, varying from five to one hundred 
and fifty miles in length. The total length of Karnes and 
Kame-plains thus far mapped is about 2000 miles. The 
map is the result of amateur explorations made at intervals 
during the past four years. 
The paper discusses the following points regarding the 
Karnes : 
1 . Ka 7 tie drift compared with glacial drift. 
The facts show that Kame material has in general been 
transported farther than the morainal material which was 
originally derived from the same locality. 
2. The Kame streams. 
The Karnes were deposited by currents flowing length- 
wise of their courses, and in all but four undecided cases 
the currents flowed southwards. The Kame streams re- 
sembled sub-aerial rivers in their meanderings, their 
branches, and in all other respects. All the long systems 
in the State are much higher at their northern than at their 
southern ends. The water of these rivers is shown to have 
flowed faster on long down slopes than on up slopes. 
There is strong reason to believe that most of the water of 
the melting glacier escaped by superficial channels, unless 
near the terminal moraine. Except near the coast there 
are in Maine almost no signs of sub-glacial streams. 
3. The external forms of Kames. 
1. The single ridge. 2. Reticulated plains, composed of 
a series of reticulated ridges with enclosed funnels or 
lakelets. 3. The solid or continuous plains, which are 
broad, flat-topped ridges, showing few or no signs of separ- 
ate ridges, and often of great height. 
4. The internal stiucture of Kames. 
Kames are of two kinds — 1. The stratified Kame, which 
is the more common type. 2. The pell-mell Kame. 
The same Kame may be stratified in one part of its 
course and pell-mell in another. 
5. Action of the sea upon the Kames. 
During the Champlain period the sea stood at a height, 
in the central parts of Maine, about 300 or 350 feet above 
the present sea level. The Kames are plainly overlain by 
the marine clays, and the sea greatly modified their form. 
The difference between the Kame that has been under the 
sea and that which has not is often very great, and conclu- 
sively proves that the Kames proper cannot have been a 
marine deposit. 
6. Topographical relations of the Kames. 
No general law of relationship between the Kames and 
the relief forms of the land can be derived from local ob- 
servations, for there are many purely local relationships. 
The only invariable rule thus far established is that the 
Kames never cross hills more than about 200 feet higher 
than the country lying to the northward. Maine is trav- 
ersed by numerous ranges of hills trending eastward or 
northeastward, and the Kame systems never cross the high 
ranges except by low passes. Low hills they cross freely. 
The inference of the writer is that the Kames were depos- 
ited when the glacier was so far melted that the higher hills 
rose above the ice surface, and hence the only escape for 
the waters southward was by the low passes. 
7. Distribution of the Kames. 
A line joining the northern extremities of the Kames is 
nearly a straight line; it trends nearly northeast and is 
roughly parallel with the coast. North and west of this 
line there are occasional short ridges of Kame origin, but 
no long systems have yet been discovered. 
(The publication of papers read before the recent 
meetings of the American Association for the Advance- 
ment of Science will be continued in our next number. — 
Ed.) 
