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Robert A. Millikan looking through microscope,
Photo by Eyre Powell Press Service. Photo ID 1.22-8
|Scientific Instruments Ancient and ModerN Part II
Celebrating 25 Years of The Caltech Archives 1968–1993
Turkish Koran, mid-sixteenth century
The preeminence of Islamic science in the Middle Ages was rivalled by achievements in the decorative arts. This exquisite manuscript with its beautiful original binding was purchased by Earnest Watson in 1957 and later given to the Institute. The wording on a stamp on the last page links this Koran to the Ottoman sultans. Although scholars have not reached complete agreement on its provenance, it has been suggested that the manuscript was presented to a mosque by Selim II, the son of sultan Suleiman the Magnificent. Selim II reigned from 1566–1574.
Universal tangent galvanometer
From Bridge Laboratory of Physics. Used at Caltech in freshman physics to demonstrate the presence of electromagnetic fields. Invented in the 1830s, the instrument is so named because the tangent of the angle of deflection of the moving coil (left) was directly proportional to the current in the fixed coil. The manufacturer was Queen and Company of Philadelphia, a prominent American firm in the second half of the 19th century.
Made of brass, in a wooden case, with plumb bob. Dated 1670 and punched with maker's initials I H. Scratched with date and initials I A, probably by the owner. Equipped with lateral sights, scaled with months, hours and degrees, and bearing celestial projections, the instrument could make topographic, astronomical and chronometric measurements. It may also have served military purposes. Purchased for the Institute by Earnest Watson in 1955.
Sector, 17th century
Brass, with Latin inscriptions. Signed by a German maker: "Gottfriedt Reiff Nori[m]b[ergae]" (i.e. of Nuremberg). Galileo's term for the instrument, which he claimed to have invented, was compasso militare e geometrico. Sectors —also called proportional compasses —were generally used, together with rulers and drawing instruments, by military engineers. This specimen has the characteristic proportional scales of Galileo's model but lacks the arc-like inset that fixes the sector into a quadrant.
Purchased for the Institute by Earnest Watson in 1955.
Manuscript version of Galileo's
"Operation of the Geometric and Military Compass"
During his early years of teaching at the University of Padua, Galileo composed brief treatises on mechanics, fortifications, cosmography, and the proportional compass. This manuscript, in the hand of a scribe, represents an early variant of the proportional compass treatise and contains substantial passages not in the first printed text of 1606.
From the library of Count Giampaolo Rocco, purchased for the Institute in 1955 by Earnest Watson with funds donated by trustee Harry Bauer.
Early edition of Benjamin Franklin's
"Experiments and Observations on Electricity"
Personally supervised by Franklin, this fifth English edition is the most correct and complete of the eighteenth-century editions of his famous work on electricity. Typical of the times, Franklin's scientific writings took the form of letters addressed to individuals, in this case Peter Collinson and others. Collinson, an English Quaker who was a cloth manufacturer and botanist, was a Fellow of the Royal Society and in that capacity introduced Franklin's letters into the Society's meetings. Eventually the letters would find their way into the Society's publication, Philosophical Transactions.
Drawing of an early electrical machine
Ascribed to Benjamin Franklin. The Franklin signature may not be authentic. On the reverse of the drawing, the following inscription in a late eighteenth-century hand appears: "This drawing was made by Benjn Franklin and represents his machine as drawn from his first model."
In the first letter to Peter Collinson, which begins Franklin's Experiments and Observations on Electricity, Franklin acknowledges receipt of the gift of "an electric tube," with instructions for rubbing it with flannel to produce a charge. Franklin and his fellows at the Philadelphia Library Company would put this tube and other apparatus to use in a series of dazzling electrical experiments. A number of electrical machines incorporating a glass tube or sphere and similar to the one in the drawing have survived. Several are presumed to have been associated with Franklin, although none is known to have been solely his invention. In the model shown in the drawing, the glass tube is mounted on a framework and turned by a crank, so that the rubbing is done by an adjustable pad from below.
Revolving azimuth quadrant
One of Tycho Brahe's instruments, described in his Astronomiae instauratae mechanica of 1598, and reproduced in a large-scale color print by Joan Blaeu of Amsterdam in 1662.
All of Tycho's instruments served to determine the positions of celestial bodies. One of his most impressive, the great revolving azimuth quadrant, was used to determine altitudes and, most accurately, azimuths. Its radius was about 1.5 meters, and Tycho claimed its scale was accurate to one-quarter of a minute of arc. The whole apparatus was mounted on an iron framework set in stone and housed in a specially designed stone crypt with a revolving roof.
Kelvin and James White electric balance
The Kelvin electric balance, patented ca 1894, uses a combination of electromagnetic attraction and repulsion and a conventional beam balance to measure electric current or voltage. The center coil at each end of the beam moves up or down in response to the magnetic fields generated by the currents flowing through the coils above and below. The deflection is then measured bymoving the sliding mass and pointer along the graduated beam to restore the balance. By varying the mass, different ranges of current or voltage can be measured on this one balance. From Bridge Laboratory of Physics.
Apparatus for demonstrating Lissajous' curves
French physicist Jules Antoine Lissajous (1822–1880) developed an optical method for studying vibration parameters. This apparatus, manufactured by the firm of Max Kohl of Chemnitz, produces visual representations of vibrations, called Lissajous' curves. The apparatus was used in Caltech's freshman physics lab.
continue on to part III of Scientific Instruments Ancient and Modern
go back to part I