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Later I acquired the barograph at the left, which is identical to the one above, apart from having a cover that lifts off instead of being hinged at the side. This one is complete and in working condition. |
| The Torricellian Barometer at the right is in the Millington/Barnard
Collection at the University of Mississippi Museum.
It was made by Newman and Son, a leading maker of instruments in England from 1827 to 1860. This time frame fits in nicely with the large number of pieces of apparatus purchased for the University by Prof. Frederick Barnard in the second half of the 1850s. The 1837 Newman Catalogue of Philosophical Instruments has no illustrations, but lists a "Standard Barometer (the most perfect instrument, as made for the Royal Society), in metal frame, with the scale and vernier of platina adjustable to the surface of the mercury, the tube from .5 to .7 in diameter, iron cistern, and capable of being made portable to travel safely ... £22" |
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In January 2003 I visited the physics department at the University of Texas in Austin. In one of the lecture preparation rooms I saw the barometer at the left, mounted on a pump plate from about 1900. |
| Barometers are hard to fit onto these pages because they are so very tall! This piece of apparatus at Hobart and William Smith Colleges in Geneva, New York, is 92 cm high, comfortably above the 76 cm needed for a mercury barometer. This set of four barometer tubes, purchased by Hobart in the late 1920s from Max Kohl of Chemnitz, Germany, is designed to show that the height of the mercury column is independent of the diameter of the glass tubes. The catalogue copy notes that the tubes are 15, 12, 8 and 6 mm in width, thus showing that the barometer reading is affected by the meniscus to a larger extent for narrow tubes than for wider tubes. The open well of mercury would not be allowed today! |
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