scholarly journals A New Absolute Determination of the Acceleration due to Gravity at the National Physical Laboratory

Nature ◽  
1965 ◽  
Vol 208 (5007) ◽  
pp. 279-279 ◽  
Author(s):  
A. H. COOK
Keyword(s):  
National Physical Laboratory ◽  
Absolute Determination ◽  
Physical Laboratory

A new absolute determination of the acceleration due to gravity at the National Physical Laboratory, England

1967 ◽  
Vol 261 (1120) ◽  
pp. 211-252 ◽  
Keyword(s):  
National Physical Laboratory ◽  
Atomic Unit ◽  
Time Intervals ◽  
Gravity Station ◽  
Absolute Determination ◽  
Physical Laboratory ◽  
Air Resistance ◽  
Definition Of ◽  
First Time

A new absolute determination of the acceleration due to gravity at the National Physical Laboratory has been made by timing the symmetrical free motion of a body moving under the attraction of gravity; it is the first time this method has been used. The moving body was a glass ball and it was timed at its passage across two horizontal planes by the flashes of light that it produced when it passed between two horizontal slits which served to define each plane optically, the ball focusing light from one of the slits, which was illuminated, upon the other slit which had a photomultiplier placed behind it. The separation of the two planes defined by the pairs of slits was measured interferometrically and referred directly to the international wavelength definition of the metre, while the time intervals were measured in terms of the atomic unit of time scale A l. The value of gravity as reduced to the British Fundamental Gravity Station in the N. P. L. is 981 181.75 mgal, s.d. 0.13 mgal (1 mgal = 10 -5 m/s 2 ). Systematic errors, are believed to be very small; this is particularly true of the error due to air resistance. The main contribution to the observed scatter of the results comes from microseismic disturbances. The new result is 1.4 mgal less than that obtained at the fundamental station by J. S. Clark (1939) using a reversible pendulum . It is very close to the mean of a number of recent absolute determinations by other methods, but this may not be very significant because the uncertainties of those determinations and of the comparisons between the sites at which they were made and the present site are not less than 5 times the standard deviation of the new result.

scholarly journals Gordon Brims Black McIvor Sutherland, 8 April 1907 - 27 June 1980

1982 ◽  
Vol 28 ◽  
pp. 589-626 ◽  
Keyword(s):  
Molecular Structure ◽  
Critical Time ◽  
Active Role ◽  
The United States ◽  
National Physical Laboratory ◽  
Andrews University ◽  
Left Behind ◽  
Active Life ◽  
Physical Laboratory

As a scientist Gordon Sutherland made, at a critical time, a major contribution to the transformation of infrared spectroscopy from a research technique practised in few laboratories into a powerful and widely used method for analysis and for the determination of molecular structure. A physicist by training, he was happy to be described as a chemical physicist or a biophysicist in relation to different aspects of his researches. Later in his career he was a successful Director of the National Physical Laboratory and then Master of Emmanuel College, Cambridge. He played an active role in British science policy. He died on 27 June 1980, in his seventy-third year, some 3 years after his retirement from the Mastership of Emmanuel College. Although after his graduation from St Andrews University Sutherland spent most of his active life in England or in the United States, he always retained the accent of a Scot, and a very deep affection for his native country. In a characteristically thoughtful way, Sutherland left behind a brief account in his own words of the earlier part of his life and career. A number of substantial quotations from his autobiographical document are included in this memoir.

scholarly journals The thermal and electrical conductivity of a single crystal of aluminium

1927 ◽  
Vol 115 (770) ◽  
pp. 236-241 ◽  
Keyword(s):  
Electrical Conductivity ◽  
Single Crystals ◽  
Test Specimen ◽  
Average Diameter ◽  
National Physical Laboratory ◽  
Present Communication ◽  
Uniform Size ◽  
The Third ◽  
Physical Laboratory

The recent work of Carpenter and Elam on the growth of single crystals of large dimensions has rendered possible the study of the physical constants of single crystals of the commoner metals, and the present communication describes the determination of the thermal and electrical conductivity of aluminium in the form of an isolated crystal. The form of the crystal investigated is shown in fig. 1. This crystal had been prepared at the National Physical Laboratory employing the technique described by Carpenter in “Nature,” p. 266, August 21, 1926, which briefly is as follows:— The test specimen is machined and subjected to three treatments, thermal, mechanical, and thermal. The first treatment is necessary to soften the metal completely and produce new equiaxed crystals of so far as possible uniform size, the average diameter being 1/150 inch. The second consists in straining these crystals to the required amount, and the third in heating the strained crystals to the requisite temperature, so that the potentiality of growth conferred by strain could be brought fully into operation.

Address of the President, Professor P. M. S. Blackett, C.H., at the Anniversary Meeting, 30 November 1966

1967 ◽  
Vol 167 (1006) ◽  
Keyword(s):  
National Physical Laboratory ◽  
Simple Approach ◽  
Ionic Crystals ◽  
X Ray Diffraction ◽  
Complete Structure ◽  
Principal Role ◽  
X Ray ◽  
Physical Laboratory ◽  
Royal Institution

The Copley Medal is awarded to Sir Lawrence Bragg, O.B.E., M.C., F.R.S. Bragg’s career has precisely coincided with the growth of a major field of science—the X-ray diffraction analysis of crystal structures. This had its beginning in his own early researches, and he has throughout played a principal role by his leadership at a series of laboratories, at Manchester, at the National Physical Laboratory, at Cambridge and at the Royal Institution, and in many other ways. He was the first to determine the atomic arrangement in a crystal (sodium chloride), and this work marked the introduction of a technique which has since been successfully applied to increasingly complicated molecules, culminating in the complete structure determination of the protein lysozyme at the Royal Institution a year before his retirement. Bragg has been prominent in the development of methods, beginning with the Law named after him; he also pioneered or encouraged the application of these methods in several fields—ionic crystals, elementary oxides, silicates, metals and proteins. The striking characteristic of Bragg as a scientist has been his direct and simple approach to complicated physical situations; his solutions of problems have a lucidity and simplicity which, in retrospect, make one forget how baffling they often seemed in advance.

scholarly journals On the determination of the absolute unit of resistance by alternating current methods

1912 ◽  
Vol 87 (597) ◽  
pp. 391-414 ◽  
Keyword(s):  
Lower Order ◽  
Alternating Current ◽  
National Physical Laboratory ◽  
Mutual Inductance ◽  
Electrical Circuits ◽  
Physical Laboratory ◽  
Absolute Measure ◽  
The Absolute ◽  
Set Up

1. Introductory .—Recently at the National Physical Laboratory we have constructed a standard of mutual inductance of novel type, whose value has been accurately calculated from the dimensions. This inductance has formed the basis for the determination of the unit of resistance in absolute measure by two different methods, in both of which alternating current is employed. Although there is no doubt that the accuracy attainable by these methods could be increased by greater elaboration of the apparatus used, the results already obtained seem to be of sufficient interest to warrant publication. It should be mentioned that the accuracy here aimed at was of a considerably lower order than that contemplated in the determination of the ohm by the Lorenz apparatus which is at present being carried out in the laboratory. For the experiments here described, no apparatus was specially constructed, but use was made of instruments which had already been designed and set up for the measurement of inductance and capacity. I shall first give a brief description of the standard inductance and then pass on to the methods and results. 2. Standard Mutual Inductance .—The design of the mutual inductance has already been described. The electrical circuits have the form and arrange­ment shown in section in fig. 1.

scholarly journals The optical determination of high metallurgical temperatures - The melting point of iron

1930 ◽  
Vol 129 (809) ◽  
pp. 91-114
Keyword(s):  
Melting Point ◽  
Molten Metal ◽  
National Physical Laboratory ◽  
Optical Pyrometer ◽  
Chemical Attack ◽  
Physical Laboratory ◽  
Thermal Changes ◽  
Refractory Crucible ◽  
Optical Determination

The present investigation has been carried out in the Metallurgical Department of the National Physical Laboratory in order to adapt the optical pyrometer to the estimation of the fusion temperatures of materials of high purity and high melting point and of substances of corrosive or volatile nature. Melting points and thermal changes in the solid state at high temperatures are generally determined by means of platinum thermocouples which are protected from the molten metal or its vapour by insertion in a refractory sheath. Contamination of the molten metal is frequently occasioned by chemical attack which takes place between the metal and the refractory crucible or couple sheath. This is particularly marked when the refractories contain siliceous material.

scholarly journals On the effect of the form of the transverse section on the frictional resistance to the motion of an elongated body parallel to its length through a fluid

1915 ◽  
Vol 92 (636) ◽  
pp. 144-157 ◽  
Keyword(s):  
Eddy Currents ◽  
Transverse Section ◽  
Practical Importance ◽  
Frictional Resistance ◽  
National Physical Laboratory ◽  
Cornell University ◽  
Physical Laboratory ◽  
Series Of Experiments ◽  
The Subject

1. The great increase in tire lengths of the parallel mid-bodies of recently constructed submarines and airships has raised into prominence the question of the frictional resistance of such elongated bodies moving parallel to their length through fluids, like air and water, whose viscosities cannot be neglected. This resistance increases as the length increases, and benefits comparable with the head and tail resistances, which for short bodies constitute nearly the whole resistance. In general, the problem of greatest practical importance is the determination of the frictional resistance when the motion is rapid enough to produce eddy currents in the fluid, but the difficulties in the way of a general theory of eddy current motion have presented a solution being reached. The simpler problem of the resistance offered by the walls of a circular pipe to the turbulent flow of viscous fluid through the pipe formed the subject of extensive series of experiments by Saph and Schoder, of Cornell University, and by Stanton and Pannell at the National Physical Laboratory.

AN IMPROVED INTERFEROMETER FOR DETERMINING PARALLELISM ERRORS IN LONG END-GAUGES

1947 ◽  
Vol 25f (3) ◽  
pp. 242-259
Author(s):  
L. Graham Turnbull
Keyword(s):  
Mechanical Design ◽  
National Physical Laboratory ◽  
Physical Laboratory ◽  
Specialized Technique ◽  
End Gauges ◽  
The Difference

This paper describes an interferometer designed for the determination of the parallelism of the working faces of end-gauges up to 24 in. in length. An instrument for this purpose, but which required somewhat highly specialized technique in the course of its construction, had been previously designed by the National Physical Laboratory. Using optical principles the same as those of the British instrument, another of an entirely new mechanical design has been constructed by the National Research Laboratories, Ottawa. This new interferometer incorporates kinematic principles and a number of interesting features to permit easy adjustment and operation to the very fine limits necessary. By the addition of a sensitive level vial to this instrument, the difference in length of nominally equal end-gauges can be determined to an accuracy of 1 or 2 × 10−6 in.

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