62 
THE SCIENTIST. 
sence or sciircity of trees is the essential 
distingiiisbiiig characteristic. The main- 
tenance of these prairies, and probably 
also their origin, maybe explained as due 
to a combination of causes ; namely, the 
alternation from an extremely cold, wet 
soil daring the rainy season, to a dry, 
hard soil in the dry season, and further 
the periodic recuri-ence of prairie fires 
which shrivel such young tree growths 
as overcome the obstacles inherent in the 
soils." 
A NiLES, Mich., correspondent wi-ites 
t() the Chicago Tribune as follows on 
the duration of the lightning flash. 
" Notwithstanding all the authorities 
teach, without exception, as far as 1 
know, that the flash is instantaneous, it 
can easily be shown without resorting to 
the camera or any other apparatus that 
it is not so. in case of a thunderstorm 
step into a dark room or corner where 
nothing can be seen except as it lightens 
and slowly move the hand in a circle of 
six or eight inches. At each flash the 
hand will plainly be seen in motion. If 
it were instantaneous the hand would ap- 
pear stationary. We are told that a horse 
trotting or a wheel in motion appears 
as standing still when observed by the 
lightning flash. I have tried the ex- 
periment of turning an electric machine 
during a thunderstorm. When a spark 
passes, the disc always appears station- 
ary, while by the flash of liglitning it is 
alwaj'S seen to be in motion.'' The cor- 
respondents experiments and conclusions 
are based upon the sense of sight. To 
test the fallacy of his conclusion simply 
look at a wheel revolving so fast that 
the spokes cannot be seen. Shut the eyes ; 
the instant they are opened all the 
spokes in the wheel are visible, and 
for an instant appear to be stationary. 
The Academy of Science now has per- 
manent quarters at room 200 Baird Build- 
ing at the Southwest corner of Sixth and 
Wyandotte Streets. The meetings are 
held every alternate Tuesday evening, 
beginning proniptly at eight o'clock. 
All are cordially invited to attend. In- 
tei-esting programmes are always pro- 
vided. The dates for the next few 
months are as follows : — Tuesday eve. 
April 7th and 21st, May 5th and 19th and 
June 2nd, IGth and 30th. 
Our exchanges are at liberty to make 
extracts from our columns or publish 
articles in full. In each case, howevei-, 
we expect proper credit. A majority of 
the articles published in the Scie]stist 
are written especially for us, and a pub- 
lisher wlio uses them without proper 
credit is guilty of piracy. The paper 
referred to in this instance, hails from 
Denver, and if the ofience is repeatetl, 
we will not hesitate to publish names. 
We are indebted to Prof. F. M. 
Webster, for Bulletins No. 2") and 83 of 
Purdue University Agricultural Experi- 
ment Station of Indiana and for a pam- 
phlet Insecticides and their Applica- 
tion." 
The flrst ai-ticle in this month's 
Scientist, cannot help but be of genei-al 
interest, coming as it does from the 
grandson of the late Professor Morse. 
While v^ry brief it never-thc-less con- 
tains several facts never before pub- 
lished. 
MSS. Eeceivi'd. 
The Great Blue Heron, By Di-. W. S. 
Strode, Bernadotte. Ills. 
Clouds-Burst in xirizona, By John 
D. Parker, M. S. A., Fort Bowie, Ai-izona. 
Ethnology, Ancient Implements. Illus- 
trated, Professor Edwin Walters. 
Drawing for Photo Reproduction, illus- 
trated. By Roger Cunningham. 
Interesting articles are also in prepai-a- 
tlon, by Hon. Warren Watson and Mr. 
D. (]. Jordan, besides several papers 
which have recently been read before the 
Academy of Science. 
