122 YOUNG 
and forward in a straight line, or wliirl 
it round in a circle. If the motion 
be sufficiently slow the fiery point will be 
visible at every portion of its path, but if 
it completes the circle or returns along 
the straight line in less than the eightli 
part of a second, it will appear as a line 
of light in the one case, and a circle in the 
other. The cause of this is that the eye 
again obtains a view of the burning point 
at the commencemcDt of the line or circle 
before the image produced by its first ap- 
pearance there has faded away. It is this 
fact which renders it so difficult to obtain 
a clear view of objects in motion. Take 
the case of trotting horses, for example. 
Hitherto it has been impossible to analyze 
their motions, and the most extraordinary 
theories have been propounded in regard 
to the matter. Fortunately, however, pho- 
tography has come to our aid, and a few- 
years sini.-e, in San Francisco, Watron 
took a series of photographs which were 
so instantaneous that the positions of the 
limbs at different points of the step were 
quite clear and distinct. This Avas due to 
the fact that the plates used required 
such a short time for exposure that the 
limbs did not move through an apprecia- 
ble space during the interval. More re- 
cently, M. Maybridge, of Paris, has taken 
photographs so rapidly that he has made 
six pictures during a clown's leap, each 
picture showing the acrobat in a different 
position. The time required to take one 
of these photographs has been proved by 
M. Marbridge to bo less than the 1-lOOth 
l)EiYt of a second. 
One of the most remarkable i)hoto- 
graphs that has come under our observa- 
tion is that taken under the direction of 
Gen. Henry L. Abbott, U.S.A., in charge 
of the Engineer School of Application, 
Willet's Point, K. Y. It became neces- 
sary, one d'iiy, at Willet's Point to destroy 
a worthless mule, and on the 6tli of last 
June the subject was made the occasion 
of giving useful instruction to the mili- 
tary class there stationed. The mule was 
placed in proper position l^efore a photo 
camera and duly focussed. Upon the ani- 
mal's forehead a cotton bag was tied con- 
taining six ounces of dynamite. The 
slide of the camera was supported l)y a 
SCIENTIST. 
fuse; the camera fuse and the dynamite 
on the mule's head being connected in the 
same electrical circuit, as shown by the 
wires in our engraving. On pressing the 
key so as to send the electricity through 
the wires, both the fuse and the dynamite 
were simultaneously fired; the camera 
slide and the head of the animal fell 
nearly together. The photo sensitive 
plate was impressed with a picture of the 
headless creature, still standing, before 
its body had time to fall. 
Fig. 1 of our illustrations, for which 
we are indebted to the courtesy of the 
Scientific American, shows the animal, 
camera and electrical wires in position 
for firing. Fig. 2 shows the appearance 
of the animal after the explosion, as taken 
on the photo plate. Here it will be ob- 
served that the head has been shattered 
and blown to one side, hanging by the 
merest shred of skin. The shock lias, 
however, been transmitted to the entire 
muscular system of the animal, as will be 
seen by the appearance of the tail and t he 
hind limbs. One of the most singular rir- 
cumstances, however, is the fact that the 
fragment of the halter, by which the mule 
was fastened to the stake, has not had 
time to fall, but remains standing as if it 
were a stiff rod. 
Rubber-Headed Tacks. 
A Xow England firm have patented and are 
manufacturin*^ a rubber-headed taclc whose 
uses are multifarious. As an insulator for sew- 
ing machines they are largely used by the lead- 
ing manufacturers, and are easilj'- and quick Ij^ 
applied. For household uses they are placed in 
the backs of chairs to prevent damage to walls ; 
in the ends and sides of door steps ; in rabbets 
of large folding doors; on lids of pianos; in 
rabbets of rattling windoAV frames, and, in fact, 
anywhei-e to overcome the nuisance of rattling. 
Car manufacturers use them to deaden noise 
and avoid aljrasion of polished surfaces. Car- 
riage mamifacturers apply them to stop the 
rattling of window frames and doors, and for 
glass frames to drop upon on the inside of 
doors. Book manufacturers place them on the 
corners of large books to protect the binding. 
In schools, slate frames and rattling desk 
lids demand them. On billiard cues they are 
used, and obviate the use of chalk. Indeed, 
there is hardly any limit to which this useful 
article may not l>e applied. 
