6i8 



NATURE 



[February b, 19,13 



observations on both sides. In the case of 

 properly selected stars at twilight, morning and 

 evening, this error can always be corrected ; and 

 in obtaining the latitude at noon, b)' the sun's 

 meridian altitude, it can also be eliminated if the 

 sun is high enough to allow its altitude to be 

 obtained by the north as well as the south horizon. 



If observations of one heavenly body are alone 

 obtained, the precise position of a vessel is always 

 open to doubt, as an allowance has to be made 

 for the change in the ship's position, for the time 

 elapsed betvifeen the observations for latitude and 

 longitude. This necessitates an allowance for 

 tide and current, which is always uncertain. 



(2) Lieut. Radler de .'\quino's work is simply an 

 amplification of a problem which has been taught 

 in some navigational schools for more than 

 sixty years and was propounded originally by 

 Captain Thomas H. Sumner, a United States 

 shipmaster, in 1837, as properly stated in a foot- 

 note on page ix. of the introduction to this work. 

 It is based simply on the fact that if a line be 

 drawn from the centre of the earth to any heavenly 

 body, at the point where that line cuts the earth's 

 circumference the altitude of that heavenly body 

 will be 90°. If a radius of the earth be taken 

 10° from the first line and a circle be described 

 on the earth's surface, at every part of that circle 

 the altitude of that heavenly body will be 80°, 

 &c. When, therefore, an altitude of a 

 heavenly body is taken, the observer is on a circle 

 on the earth's surface at every point of which the 

 altitude will be exactly equal to the altitude he 

 has observed, and his position on that circle will 

 be where the true bearing of the heavenly object 

 cuts the circle. 



The circles on the earth's surface have such a 

 large radius that they can be treated for short 

 distances as straight lines, by assuming the 

 tangent to the circle to be a line of position on 

 which a ship is situated. 



In the days of sailing ships, or of auxiliary 

 powered steamers, these lines of position were used 

 chiefly to obtain the latitude and longitude, as, by 

 observing the altitudes of two or more heavenly 

 bodies suitably situated, as near right angles to 

 each other as practicable, two or more lines of 

 position were obtained at the same time, and the 

 observer's position was in the spot where these 

 lines cut each other. 



In these days of fuII-powered steamers the posi- 

 tion line can be made use of to make any particular 

 point on a coast, for if the line of position runs to- 

 wards the coast a vessel has only to steam along it 

 to arrive at the point on the coast which it cuts. 

 This is not new, Ijut is only practicable in ships 

 of the present day. 



NO. 2258, VOL. 90] 



In Lieut. Radler de Aquino's book some tables 

 are given by which the problem can be solved 

 without working out the spherical triangle upon 

 which the problem is based, but as the spherical 

 triangle can be worked in about five minutes, there 

 is no particular advantage to an officer in throw- 

 ing over the system which he ^nust understand 

 and be familiar with to be a good navigator, to 

 take up another system in its place, and to crowd 

 the limited space available in ships with works 

 that are not absolutely necessary, more especially 

 as little or no time is saved by doing so. 



OUR BOOKSHELF. 



Notes on Chemical Research. An .Account of 

 Certain Conditions which Apply to Original 

 Investigations. By W. P. Dreaper. Pp. x + 68. 

 Price 25. 6d. net. 

 Mr. Dreaper is the editor of The Chemical World, 

 and his "notes" first appeared in that vigorous 

 young journal. They were well worth reprinting ; 

 for, although they have the unsystematic charac- 

 ter which the title seems to admit, they are 

 informed both by wisdom and enthusiasm and 

 cannot fail to stimulate the young workers to 

 whom they are addressed. 



Mr. Dreaper's main thesis is that the researcher 

 " must give special attention to the theoretical 

 side of his science, and train his mind to discover 

 in the recorded work of others the conditions 

 which have led to success." In delivering this 

 opinion he has in view researchers both in "pure " 

 and "applied" science. Indeed, one of the most 

 interesting points in the book is the author's oft- 

 expressed conviction that under modern conditions 

 the dividing line between these two kinds of 

 inquiry has become and will continue to become 

 less marked. It has become necessary for the 

 practical man to keep closely in touch with theory 

 and for the worker in pure science to have some 

 knowledge of industrial experience which is apt — 

 owing to the large scale of the phenomena — to 

 throw important light upon theoretical questions. 

 This view is excellently illustrated by numerous 

 examples drawn from the present state of pure 

 and applied chemistry. For the rest, it must 

 suffice to add that Mr. Dreaper presents in an 

 attractive and non-technical way a sound philo- 

 sophy of scientific inquiry. T. P. N. 



Elekirobiologic. Die Lehre von den elektrischen 

 Vorgjingen im Organismus auf moderner Grund- 

 lage dargestellt. By Prof. J. Bernstein. Pp. 

 ix + 215. (Braunschweig: F. Vieweg und 

 Sohn, 1912.) Price 6 marks. 

 Prof. Ber\st kin's " Electrobiology " is a particu- 

 larly fascinating presentation of the electrical 

 phenomena of animal and plant tissues, coloured 

 from beginning to end bv the observations and 

 ideas of its author. 



The earlier chapters, dealing with historical 

 matter and with the electrical properties of muscle, 

 nerve, &-c., lead up to his "membrane theory" 



