70 



It was not from the want of a conviction of the advantages con- 

 nected -^vith great circle sailing that, till of late, it had been so rarely- 

 used by practical men, but from the tedious length and emban"assing 

 nature of calculations requisite to determine the series of ever-changing 

 courses which a vessel must pm'sue, in order to foUow the track of a 

 great circle. 



In order to obviate this evil, I invented and computed a set of tables, 

 in 1847, which the British Admiralty did me the honour to publish, by 

 means of which the finding of these courses in succession is reduced to 

 an affair of inspection. By this means I have had the honour of intro- 

 duciug great circle saihng into general use : from which circumstance 

 it has been assumed by some, erroneously, that I have laid claim to the 

 invention of great circle sailing, and this supposed assumption of mine 

 has been apparently coufirmed by the fact of my laying claim to the 

 honour of being the originator of composite sailing, which is often de- 

 nominated great circle sailing, and to which we shaU hereafter refer. 

 In order to clear myself from the charge of assuming the honour of being 

 the inventor of great circle sailing, with which I have been frequently 

 taunted, I will read from one of the most extensively-circulated works 

 (" Weale's Rudimentary Treatise") a quotation from a lecture delivered 

 by myself to the Society of Arts : — 



" From a communication by Mr. Towson to the Society of Ails, in 

 May, 1850, it appears that, in 1495, Sebastian Cabot projected a 

 voyage across the Atlantic on this principle, with a view to the dis- 

 covery of a north-west passage to India. In 1537, in the first treatise 

 on Navigation, the system was treated of by Numez. In 1561, Cortez, 

 and after him Coignet and Zamai'amo, advocated the adoption of great 

 circle sailing." 



From these observations it wiU be evident that I am not chargeable 

 with the desire to claim the unmerited honour of being the inventor of 

 great circle sailing. 



Before we advance further in the investigation of the subject, it wiU 

 be necessary to make a few remarks on the nature of Mercator's sailing. 

 In order that the sphere should be drawn on a plane, it is necessary to 

 distort the surface. Those regions towards the pole have to be dis- 

 tended for this purpose. In thus distorting the earth's surface, the 

 shortest route is made to appear as circuitous ; and the circuitous route, 

 by a parallel of latitude, is represented by a straight line. If two places 

 do not differ in longitude more than 30 or 40 degi-ees, the error of 

 Mercator's chart is not very perceptible. In crossing the Atlantic, it 

 differs from the great circle route not more than 100 miles in practice ; 



