The Portland daily press. [volume] (Portland, Me.) 1862-1921, 1883-08-17
cleveland Leader.l

well-known worker with that instrument.
swell, if you IRE ready to take notes
enough to fill book, all right. warn you,
though. that it's big subject
"You can tell few things about it that
will be of interest. In the first place what
does an instrument like that cost?'
about 500 or $500. A good enough one
for ordinary work can be procured for $50
or $50; from that all the way up"
"How many times does your microscope
magnify?'
That question is the shibboleth of mi
croscopy. The uninitiated always ask that
question, and always suppose that the high
Ell. the power capable of being used the more
valuable the instrument. All nonsense l
have used as high as 100000 diameters, but
the result was not nearly SO satisfactory as
if had used $1,000 The ordinary work for
which physician would use microscope
would require from 100 to 500 diameters on
ly, while special work can be done with ease
with from 1000 to 5000 diameters power,
There's point you must look out for in
buying microscopes from ordinary instru-
ment sellers. half the time they will con-
= found the times and 'diameters.' The di-
aEeter, as of course you know, is the dis
lance across the object, and if an object is
magnitied 500 diameters it is magnified 25O,-
600 times, or just the square of the diameter,
You can easily see that there is quite diff
ference in point of fact between the two di-
mansions in measurement, and any confu-
sion of the terms is apt to mislead.
is asfn chiper 10 ,n+a ,r,,l
rance in which the general public is steeped
with regard to the microscope. Ask most
any respectable citizen of only ordinary edu-
cation what it is makes the microscope mag
nifty, and it is ten to one, if he ever even
gave the subject thought, he will say that
1t is the peculiar quality of the glass in the
lenses. He will be rather suspicious of his
informant's veracity when he is told that it
is the degree OF curvature which makes the
glass magnitier. To be sure, there is some
shadow OF truth in the supposltion that
peculiar kind of glass is used. There are
two kinds of glass used which tend TO cor
rect each others inaccuracies. The glass is
cooled so gradually, and stirred so constants
ly, that it is perfectly homogeneous, and
there are no streaks of uneven density and
no bubbles or other flaws. Common, cheap
microscopes have any kind of glass for lenses
even to window-glass.u
what is the primitive microscope?v
"a drop OF water. Not bad one either,
only il is inconVenient to work. The early
microscopes were immense things, some Of
them being six feet long and having great
/uncorrected lenses two or three inches in di-
ameter, being in fact young telescopes. With
every year the differentiation from the tele-
scope has been more and more marked
That suggests another popular notion which
is as incorrect as popular notions are apt to
be. The average citizen has no conception
of such thing as a focus to microscope
He has an idea that if the microscope is
simply pointed at an object it can be seen as
well as not. He seems to think that it can
be used for star-gazing In fact, have had
people ask me, And can you look at the
stars with this thing, too?' y
You spoke moment ago about the yari-
GUS magnifying powers; how can you tell
how high power is used? Is it marked on
the lenses?'
mo fine instruments make any specific
claim for powers. The operator himself fig
ures out each time how high a power he
uses. Every microscopic has a micrometer
which he uses to measure the power. Here
is one. 1t is a little flake of glass $1,000 Of
an inch in thickness cemented on to slide
which is perhaps fiftieth of an inch thick,
On this are engraved with damond-point-
ed tool lines drawn at intervals of the one
thousandth of an inch apart. When it is
desired to calculate the power being used,
the tube of the microscope is put in a hori-
zontal position, the eye-piece is taken out,
and instead peculiarly shaped prism is in
serted, which is SO arranged that the rays
from the microscope enter the upper half of
the pupil of the eye, while with the lower
half sheet of paper can be seen which is
placed ten inches from the eye. The lines
are then traced on the paper as they appear
to The observer. The distance betN cen the
liranc ic md ivi nd hut I,a
actual distance between the mic ometer
lines, and the result is the magnifying pow
er.
"The value of a microscope consists in its
power to show things distinctly at all pow
ers. To test this plate of glass is engraved
Id the same manner rs the micrometer with
the exception that the lines are not SO deep,
and they run in bands. Here is test-plate
ruled with lines varying from 5000th TO l.
150,000th of an inch apart
"Can the finest lines be seen?'
mo. 1t is simply an article of faith that
they exist. No one has seen them yet. The
man who made the plates knows he set the
feed to cut that many lines to the inch. 1t
was within the last few years that the posi-
biGty of engraving 10000 lines to the inch
was doubted. myself have seen 10000,
and one man has claimed to be able to see
154, ZOO, bat it is a little doubtful. These
micrometers have to be engraved very care
fully, as mans life and death may depend
upon the exactitude of their measurement.
Prof. Rogers, of Cambridge Observatory, had
a machine made to engrave the lines. 1t
cost him 81 800, and took three years and
half to finish"
"What do you mean by saying that mans
life or death may hang on the exact meas
urement of line?'
Suppose there is a murder trial. The
evidence of microscopic is required to
show whether certain stains Of blood are of
human origin or not. There is no differ
ence in the shape Of the constitution of the
blood corpuscles in man or the lower warm
blooded animals; the only difference is that
of size, and that has to be determined by the
average corpuscle rather than one alone.
The blood Of rabbit may have some cor
pusces in it as large as some in human
blood, but the average is smaller. The only
family of mammals that does not have round
corpuscles is the camel family. Tie blood
OF birds and reptiles has oval corpuscles with
well defined nuclei or spots in the center"
Tell me some more popular errors in re-
gard to the microscope"
zone very odd one and very common one
is that every drop of water we drink is teem-
ing with animal life. There never was a
greater mistake. 1t is very rarely, indeed,
in lake water that animalculae are to be
found. If little bit of grass, or shred of
meat, or any organic matter be left in water
for two or three days, there they can be
found. 1t is supposed that peculiar kind
of organism like cells can be found in vine
gar. 1t may be that way back in the coun-
try, where they make vinegar out of apples,
and not of aquafortis, there may be some,
but they don't seem to thrive in city vinegar.
Another thing, people think that hairs are
hollow. The hair is no more hollow than
fence post, and the coloring matter instead
of being filled in tube, is mixed up in the
cells of the hair The mistake never would
nave occurred if it was recollected that the
hair is but modification of the epidermis.
Then there is another idea that the human
skin is as full of pores as SPONGE"
The fallaey of this idea was demonstrated
by the microscopists taking slice with
razor off his hand and putting it on a slide.
Inc reporter was surprised to find that the
pores were very scarce indeed, appearing to
be about fiftieth of an inch anart esassl