672 SCIENCE PROGRESS 



general methods of procedure, quantitative accuracy, adjustment of observations, 

 etc. — topics that are often merely mentioned in the introduction or appendix of a 

 laboratory manual, but that need laboratory work and drill quite as much as the 

 measurements of the individual quantities that the student will take up in his later 

 work." Again, " the object of a course in the theory of measurements is not only 

 to give a certain knowledge of the scientific facts that are studied, but also to 

 develop the thinking and reasoning powers and to furnish the special kind of 

 mental training that results, in the first place, from practice in making various 

 kinds of measurements with particular care for their accuracy, and, in the second 

 place, from the consideration of accuracy in its quantitative aspects, — from realising 

 that accuracy itself can be made a subject of measurement, that there are relative 

 degrees of accuracy, that accuracy is important in one place and means only a 

 waste of effort in another, that absolute accuracy is an impossibility, that a 

 measurement by itself is of much less value than when accompanied by a state- 

 ment of its precision." This is an admirable book, and it will be found very useful 

 in a mathematical or physical laboratory. 



After an introductory chapter, there are chapters on weights and measures, 

 angles and circular functions (in which a " function " is defined on p. 47 to be a 

 quantity which has a definite value for each particular value of the variable, so 

 that apparently the inverse functions are not " functions "), significant figures (we 

 read on p. 60 that " the figures of which a number is composed, except for one or 

 more consecutive ciphers placed at its beginning or end for the purpose of locating 

 the decimal point, are called its significant figures "), logarithms, small magnitudes 

 which may be neglected in approximations, the slide rule, graphical representations 

 by curves, curves and equations, graphic analysis, interpolation and extrapolation , 

 coordinates in three dimensions, — including the construction of a contour map, — 

 accuracy, the principle of coincidence, measurements and errors, statistical 

 methods, deviation and dispersion, the weighting of observations, criteria of 

 rejection, the method of least squares, indirect measurements, and systematic and 



constant errors. 



Philip E. B. Jourdain. 



ASTRONOMY 



The Astronomical Observatories of Jai Singh. By G. R. Kaye. [Pp. viii + 

 153, with 27 plates and one map.] (Archaeological Survey of India, New 

 Imperial Series, vol. xi. Calcutta : Superintendent Government Printing, 

 1918. Price 23s.) 



The extremely interesting volume which Mr. G. R. Kaye has compiled on the 

 astronomical observations of Jai Singh is the result of a tour of the observatories 

 of Delhi, Jaipur, Ujjain, and Benares, which was arranged through the kindness 

 of the Director-General of Archaeology and the Educational Commissioner of the 

 Government of India. The volume is primarily a tour report for the Archaeo- 

 logical Department, and from the point of view of the purely astronomical 

 reader it suffers somewhat from the restrictions necessarily imposed by this fact. 

 The general reader, however, gains on account of the descriptive nature of the 

 book. 



Jai Singh, Maharaja of Jaipur, was born in a.d. 1686, the year in which 

 Newton's Principia was completed, and eleven years after the founding of 

 Greenwich Observatory. He succeeded to the Amber territory in 1699, and was 

 later appointed Governor of the provinces of Agra and Malwa. He died in 1743 

 after a troubled reign, in a period when anarchic conditions prevailed. His 



