Callendar, Hugh Longbourne

(b. Hatherop, Gloucestershire, England, 18 April 1863; d. Ealing, England, 21 January 1930),

physics, engineering.

Callendar received his early education at Marlborough. After classical and mathematical studies at Trinity College, Cambridge, from which he graduated both in classics (1884) and in mathematics (1885), Callendar became a fellow there in 1886. After serving as professor of physics at the Royal Holloway College, Egham (1888–1893), Callendar accepted an appointment as professor at McGill University, Montreal (1893). In 1898 he returned to England as Quain professor of physics at University College, London; in 1902 he became professor of physics at the Royal College of Science (in 1907 incorporated in the Imperial College of Science and Technology), a post he held until his death. In 1894 Callendar was elected a fellow of the Royal Society. He received the Watt Medal of the Institution of Civil Engineers, for his work with Nicolson on the laws of condensation of steam, in 1898; the Rumford Medal of the Royal Society in 1906; and the Hawksley Gold Medal of the Institution of Mechanical Engineers, for his investigations of the flow of steam through nozzles and throttles, in 1915.

Callendar’s scientific work was mainly in the field of experimental science, particularly heat and thermodynamics, in which he devised and carried out accurate methods of measurement and designed new apparatus. Especially important were his introduction of the platinum resistance thermometer as a new standard of accuracy for physical and engineering measurements and his investigations on the thermal properties of water and steam.

Callendar’s first publication, which was communicated to the Royal Society in 1886, dealt with platinum resistance thermometry. Sir Humphry Davy had discovered the dependence of the electrical resistance of metals on temperature (1821), and the German engineer Ernst Werner von Siemens had used this phenomenon in the construction of a platinum resistance thermometer (1861). Callendar made elaborate experiments on this subject at the Cavendish Laboratory in Cambridge, in which he compared the platinum resistance thermometer with Regnault’s normal air thermometer and from which he deduced that the resistance of a properly made platinum wire can be related to the reading of the air thermometer by a parabolic formula that was accurate within 1 percent. In a later paper (1891), Callendar gave practical suggestions for the construction of stable platinum thermometers with mica insulation to avoid strains in the platinum wire. The use of the platinum thermometer as a laboratory instrument instead of the more complicated air thermometer was especially important for the research worker as an easy and accurate method of measuring temperature. It also gave the engineer a convenient and practicable method of heat regulation in industrial operations. Callendar also added an automatic recording bridge to the platinum thermometer (1898).

In 1899 the Committee on Electrical Standards, which was headed by Lord Rayleigh, accepted Callendar’s proposals for a standard scale of temperature based on the platinum thermometer. The platinum thermometer is now the recognized international means of interpolation between the boiling point of liquid oxygen (—182.97°C.) and the melting point of antimony (630.5°C). Above the latter temperature a thermocouple is used.

Callendar used the platinum thermometer in a number of investigations. In a joint study with Howard Turner Barnes he determined the variations, with temperature and with strength of solution, of the electromotive force of different forms of the Clark standard cell (1898). With John Thomas Nicolson he determined the temperature of steam expansion behind a piston (1897). In the latter investigation clear evidence was obtained for the existence of steam in a supersaturated state, a state already known at that time but considered of negligible importance in the field of steam engineering.

During his stay in Montreal, Callendar developed his method of continuous electrical calorimetry, the first experimental application being the measurement by his assistant Howard Turner Barnes of the specific heat of water between its freezing point and boiling point, together with a determination of the mechanical equivalent of heat (1902). With this continuous-flow method a new way was opened for measuring specific heats of liquids, while the large corrections for heat capacity of the apparatus that were necessary in normal calorimetry were reduced to a minimum.

At McGill University, Callendar also studied engineering problems connected with steam turbines and internal combustion engines. With John Thomas Nicolson he made many valuable experiments on the heat of transmission and on leakage losses from steamengine cylinders. Callendar did important work on the properties of vapors. With his continuous-flow method he determined the specific heat of steam and its variation with the pressure. He also measured the total heat of steam and the specific heat of water at any pressure and temperature. In 1900 he studied the thermodynamic properties of gases and vapors, as deduced from a modified form of the Joule-kelvin equation, with special reference to the properties of steam; in his report he first put forward his equation for an imperfect gas, which has been very useful in representing the properties of steam. This paper formed the basis of Callendar’s subsequent work on steam, which led him to the formulation of his steam equation and the publication of Callendar Steam Tables (1915 ff.), which give the properties of steam up to and beyond the critical pressure.

Besides his work on thermometry and vapors, Callendar wrote a number of papers on such subjects as the osmotic pressures of solutions (1908 ff.), the absolute expansion of mercury (with Herbert Moss, 1911 ff.), and the determination of the boiling point of sulfur (with Ernst Howard Griffiths, 1890, and Herbert Moss, 1912). In conjunction with the staff of the Air Ministry Laboratory, Callendar published papers on dopes and detonation (1925, 1926). In 1926 he published on the cause of knock in gasoline engines and the effect of antiknock compounds on engine knock.

Callendar was the inventor of a system of shorthand which was in fairly general use in some parts of the former British colonies. In 1889–1890 he published A Manual of Cursive Shorthand and A System of Phonetic Spelling Adopted to English.

BIBLIOGRAPHY

I. Original Works. Callendar’s scientific papers include “On the Practical Measurements of Temperature: Experiments Made at the Cavendish Laboratory, Cambridge,” in Philosophical Transactions of the Royal Society, 178A (1887), 161–230; “On the Construction of Platinum Thermometers,” in Philosophical Magazine, 32 (1891), 104–113; “On a New Method of Determining the Specific Heat of a Liquid in Terms of the International Electrical Units,” in British Association Reports (1897), pp. 552–553, written with H. T. Barnes; “Experiments on the Condensation of Steam,” ibid. pp. 418–424, written with J. T. Nicolson; “On the Bridge Method of Comparing Low Resistances,” in The Electrician (London), 41 (1898), 354; “An Alternating Cycle-Curve Recorder,” ibid., 582– 586;“On the Variation of the Electromotive Force of Different Forms of the Clark Standard Cell With Temperature and With Strength of Solution,” in Proceedings of the Royal Society, 62 (1898), 117–152, written with H.T. Barnes; “On the Law of Condensation of Steam Deduced From Measurements of Temperature-Cycles of the Walls and Steam in the Cylinder of a Steam-Engine,” in Minutes of Proceedings of the Institution of Civil Engineers (London), 131 (1898), 147–206, written with J. T. Nicolson; “Proposals for a Standard Scale of Temperature on the Platinum Resistance Thermometer,” in British Association Reports (1899), pp. 242–243; “Notes on Platinum Thermometry,” in Philosophical Magazine, 47 (1899), 191–222; “On a Practical Thermometric Standard,” ibid., 48 (1899), 519– 547;“Note on the Variation of the Specific Heat of Water Between 0° and 100° C.,” in The Physical Review, 10 (1900), 202–214, written with H. T. Barnes; “On the Thermodynamical Properties of Gases and Vapours as Deduced From a Modified Form of the Joule-Kelvin Equation, With Special Reference to the Properties of Steam,” in Proceedings of the Royal Society, 67 (1900). 266–286; “Continuous Electrical Calorimetry,” in Philosophical Transactions of the Royal Society, 199A (1902). 55–148; and “On the Variation of the Specific Heat of Water, With Experiments by a New Method,” ibid. 212A (1912), 1–32.

II. Secondary Literature. For obituary notes, see Engineering, 129 (1930), 115–117; Nature, 125 (1930), 173–174; and Proceedings of the Royal Society, 134A (1932), xviii-xxvi. Biographies of Callendar are in Chambers’ Dictionary of Scientists, A. V. Howard, ed. (London, 1950), col. 84; and Dictionary of National Biography, supp. 4 (1930), 152–154. Bibliographies are given in the Royal Society of London’s Catalogue of Scientific Papers, XIV (1915), 18–19 and Poggendorff, IV (1904), 214–215. 1703; V (1926), 197; VI (1936), 389.

H. A. M. Snelders