In addition to basic illumination, the physicist uses the light from lamps for its directionality and for its spectral content. And, in the case of Locatelli's lamp, the thermal radiation is what is desired. Arc Lamps are discussed separately.
   The 1916 catalogue of the L. E. Knott Apparatus Company of Boston lists this at the "Hefner Lamp, approved by the Physikalish-Technichen Reichsanstalt as the German Photometric Standard Source of Light, burning amyl-acetate." Its duty-free price was $12.50; with a certificate of calibration the price was $16.50.

   The example at the left is at Denison University in Granville, Ohio, while the one at the right in in the Greenslade Collection. They were both made by A. Brüss of Hamburg, and are marked 1904. 

   The wick is contained in the (covered) central tube of the lamp. The upright arm contains a Krüss optical flame gauge that allows the flame to reach its required height. The standardized design dates from about 1893.
   This Davy or miner's lamp in the collection of Washington and Jefferson College in Washington, Pennsylvania. 

   It is marked "John Mills/Newcastle on Tyne." The 1881 catalogue of James W. Queen of Philadelphia shows a very similar lamp priced at $4.00. 

   The miner's safety lamp, invented by Humphry Davy in the first few years of the nineteenth century, had its open flame confined by the wire gauze surrounding it, and was consequently used in coal mines where flammable gases might exist. 

 Locatelli's lamp was used as a source for experiments on thermal radiation. Thus, it was both a light and a heat source. 

   The lamp burns alcohol in the wick placed at the focal point of the polished copper reflector. There is no chimney, and the cylindrical tank holds the alcohol.

   The lamp at the left, from the Greenslade Collection, was sold by Max Kohl of Chemnitz at 14.50 marks about 1900.

   At the right is a lamp by an unknown maker in the Garland Collection of Classic Physics Apparatus at Vanderbilt University.

   The Zirconia Burner at the left produces an intensely bright and white light. Jets of oxygen and either hydrogen or illuminating gas impinge on the button at the top and are ignited. 

   This is related to the more familiar lime light, in which a block of solid lime is burned by the hot flame. I suspect that the zirconia button is longer lasting than the lime. 

   This apparatus is in the apparatus collection of Dartmouth College.

   When I first visited the collection of historic physics apparatus at Dartmouth College in October 1979, Prof. Alan King told me that this gas lamp was a Welsbach lamp. 

   A Welsbach burner operates by the combustion of a mixture of air and gas to heat a gas mantle to incandescence. Inside the Dartmouth lamp can be seen the mantle of ash, protected by the mica shade. It is thus a precursor of the familiar Coleman gasoline lantern, in which the pressurized gasoline is vaporized by passing it through a fine jet. 

   I found this light source in the apparatus collection at Dartmouth College. It appears to be a kerosene lamp in a portable holder than can either be hung up or placed on a flat surface. Its shape pleased me, and I added it to my collection of images.
   This lime-light burner is in the Jack Judson Collection at the Magic Lantern Museum in San Antonio, Texas. The connections for the oxygen and acetylene supplies are projecting to the left on the lower side of the base, and the combustion jet is pointing toward the block of calcium carbonate. 

   The apparatus is designed to slip into a projector and was made by T[homas] Hall of Boston.

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   Below is an Argand Lamp from the Jack Judson Collection in San Antonio, Texas. The writing on the chimney reads "Stork Brand/Fireproof/Made in Denmark". This gas lamp was used as a standard in France in the latter years of the nineteenth century. The burner, at the right, has twenty-two orifices to ensure complete combustion.

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