254 THE MEDITERRANEAN SEA. 



annually, which fall upon its area. The level remaining the 

 same, the- question occurs how this balance is maintained ? It 

 cannot be by efflux into the Atlantic, since the only notable 

 current in the Straits of Gibraltar is a central one, setting 

 constantly inwards from the ocean; at the average rate 

 between Tariffa and Alcagar Point, where the passage is nar- 

 rowest, of nearly three miles an hour. Halley urged, and 

 made experiments to prove, that simple evaporation from a 

 surface of this extent and in this latitude, was fully equal to 

 explain the phenomenon ; and though some of his postulates 

 are doubtful, the general conclusion may fairly be admitted. 

 It is a fractional part and local evidence of that great balance 

 or law of compensation which prevails over the globe; 

 blending together the various elements of force and action 

 into one constant and harmonious result. Whatever seeming- 

 disorders may occur in the working of these elements, they 

 so neutralise one another in time and locality as to maintain 

 unimpaired that equilibrium which, on a small scale, is often 

 vainly sought for by human labour and ingenuity. 



We must remark, however, that there is still a good deal 

 of uncertainty as to the eastward current in the Straits of 

 Gibraltar. What the deviations are from its average velocity, 

 and how produced, are points not yet ascertained. Nor have 

 we any certain proof as to a point more disputed; viz. 

 whether there be not an under-current, carrying outwards an 

 equivalent to the volume brought in from the ocean. Two 

 or three ambiguous stories of sunken ships, transported west- 

 wards, have been accepted as partial proof to this effect. 

 Stronger presumptions have been drawn from the necessity 

 of such outgoing equivalent to the surface current setting in, 

 from our knowledge of counter-currents of similar kind in 

 other oceans and seas , and from the fact observed of the 

 increasing specific gravity of the waters of the Mediterranean 

 within the Straits as their depth augments. These conjee- 



