The Birmingham age-herald., 1913-08-10
THE MOST PATIENT
/. MAN IN THE WORLD
Is a Grinder of Lenses
Named Petitdidier
EXTREME EXACTNESS
Spent Three and One Half Months in
Dark Room Grinding Lenses to
Accuracy of One Millionth
of An Inch
EXTREME EXACTNESS
From the Chicago Tribune.

From the Chicago Tribune.
| When Prof Albert A. Nicholson of the
University of Chicago was making his
investigations of spectra for which he was
awarded the Nobel prize in physics in
1907. he found himself in need of 16-inch
parallel plates ground to an accuracy of
one-millionth of an inch. It was also
necessary that he have an interferometer
enabling him to measure the differences
of lenses varying one millionth of an inch
or less, that he might obtain the true
value of the standard meter. Apparently
Dr. Michelson's computations had led
him to the impossible, and the accuracy
of their demands threatened to pass the
bounds of the practical
DIR. Nicholson was In a duandary when
he heard of one Petitdidier, called by
faculty members in the university 'the
most patient man in the world Petit
didier had been employed by the Uni
versity of Chicago to grind lenses for
the Yerles observatory telescope. Act
ing upon the advice of his colleagues,
DR.. Nicholson sought the lens grinder.
| On the door of an uninviting place at
| 5423 Lake avenue Chicago, the eminent
| physicist read the half-effaced legend
Octave L. Petitdidier," and walked in.
He was greeted kindly by nervous little
man with a big head, surmounted by a
| heavy shock of coarse black hair In
terse sentences DR.. Nicholson made
known his needs. In sentences quite as
terse Petitdidier accepted. the commission
and specified the time for the delivery
of the lenses and plates. DIR. Nicholson
was relieved, but dubious.
Worked Three and Half Months
Petitdidier set to work on the order
almost as soon as the interview closed.
He worked three and half months, 10
| hours a day, in dark room kept at a
| constant temperature. The extreme care
which it was, necessary to exercise with
| the plates and lenses almost disrupted
| the health of Petitdidier, but he turned
out the order satisfactorily and DIR. Mi
chelson was able to continue his inves-
/ legations DIR. Michelson's Investigations
startled the universe; but, Petitdidier' S
fame spread only to a select number of
| scientists.
| Petitdidier is a dealer in optics, a
grinder of parallel plates for echelon
lspectroscopes, a maker of lenses for
telescopes. Patience is the equivalent
of accuracy in his vocabulary and his
peculiar aptitude has drawn astrono-
mers and physicists of international re-
pute to his dingy little shop in Lake
avenue He is an anomaly in the
field of science. He presents the spec
tacle of an amateur developing a hob
by into an exact science in which he
alone is thoroughly proficient
Lens making is perhaps the most ex-
acting of professions known to modern
industry. The glass for the lenses
must be absolutely free from bubbles
and flaws-a condition which IS almost
impossible to attain in the huge pieces
needed for 60-inch lenses. Petitdidier
imports his glass from France and
pays a price that would make the cut
| glass merchants wish they could sell
their wares by the pound at the same
price.
Even rough shaping lenses is a prop
osition of extreme difficulty. After the
crude shaping has been done with the
die designed for the lens the glass
must be rotated thousands of times
under a chamois pad covered with a
preparation of rouge. This process
| cannot be continued for more than two
hours a day because of the expansion
of the glass resulting from friction.
! When the accuracy of the lens ap-
proaches one hundred thousandth of an
inch the real difficulties begin. There
are no instruments fine enough to
measure the inaccuracies and Petit
didier tests the surface by optical
means. Every one is familiar with the
| fact that a glass prism shows different
colors 1t is this refraction of light
| that betrays the inequalities to Pet
fiddler. Examining the entire surface
of the lens time and again for minute
spots of color that betray Inaccuracies,
he polishes here and there. slowly work.
ing the lense into perfect shape.
Profession Disease
| Petitdidier calls his profession "dis-
ease" and he has constantly to warn en-
thusiastic professors against absorption
| in the subject of the optics. He has had
seven scientists under his tutelage, but
before they progressed very far in the
work he cut short his instructions with,
| you had better cut 1t out now. 1t will
get you just like it got me. And once it
| gets you, you are done for"
| 1t was 80 years ago that the disease
got Petitdidier. He was born in VILE
magne, France, over half a century ago
and pursued classical and engineering
courses in the government college in Au-
benas, France. For two years after his
| graduation he was connected with the
engineering corps of Berderieux in the
construction of bridges and highways.
Later he entered the civil engineering
| service of the United States and built
| the lock dam at Mount Carmel H.,
which has been considered the best in
| the country.
| 1t was at Mount Carmel that Petitdidier
| first became interested in optics as an
amateur. Before long he abandoned his
post as civil engineer and delved into the
less lucrative but more fascinating work
of making lenses for telescopes. He was
called to Chicago by the University of
Chicago and has contract for making
all the university's optical instruments.
His fame in the construction of tele-
scopes resulted in his being engaged to
make lenses for the Lick, Mount Wilson,
Flagstaff and various university observa-
tories He is one of three men in the
whole world who grind parallel plates.
He has one assistant, a young man. whom
he hopes to instruct sufficiently to have
the youth succeed him in his work.
The Same Old Reason
| ID IT,