2S0 REVIEWS — GALES IN THE ATLANTIC. 



biniug the two, a diagonal movement at the will of the operator is 

 secured. 



The advantages of this plan are simply these : 1st, the lever is not 

 in the way of the operator, yet very easy of access, and the power is 

 applied as near the centre of the stage plate as it is possible for it to 

 be- 2nd, only one hand can in any case be necessary to produce 

 every motion that may be desired ; and 3rd, it is very simple, is not 

 liable to get out of order, and if it should happen to get out of 

 repair can readily be set right again. 



I may perhaps be permitted to point out another improvement in 

 this instrument, which has lately been introduced in England, and I 

 believe also in the United States. This consists of a new arrangement 

 for the coarse adjustment of focus. 



The rack and pinion movement which is always unsteady and works 

 by jerks even when most carefully constructed, is here dispensed with, 

 and instead of it a chain movement is substituted, which has the 

 advantage of being much smoother, and more sensitive, of being less 

 likely to become unequal by wear, and of being easily tightened if it 

 should cease to act, or " loose time" as it is technically called, while 

 its delicacy and smoothness admit of an exact adjustment being made 

 by its means alone, even when using high powers. 



REVIEWS. 



Gales in the Atlantic : By Lieutenant Maury. U. S. N., Washington 

 Observatory, May, 1857. 



In extending a knowledge of the physical phenomena of the 

 Atlantic Ocean, the publications of the Washington Observatory 

 under the able superintendence of the author of the " Physical 

 Geography of the Sea," stand deservedly pre-eminent. Lieutenant 

 Maury's Wind and Current Charts— an annual volume of over nine 

 hundred quarto pages accompanied by a large number of ingenious 

 and elaborately executed maps — are universally allowed to have con- 

 tributed the most essential aid to navigation. As Humboldt truly 

 states, the shortening of mnn3 r a dreary voyage may be cited as one 

 of their results. In that valuable publication, the gales of the 

 Atlantic are especially discussed ; and various explanatory 



