248 Review of Mrs. SomervUle's Connexion of the Physical Sciences. 



to be spherical } and it is observed also, that in a shower the rain-drops 

 adhere to the window, but it is not discovered that both effects depend 

 upon a similar cause, the important law of cohesion. A new law is in- 

 vented for every phsenoinenon that is observed, nor does any one observation 

 enable the probable result of another to be conjectured. 



But as the mind advances in knowledge, it advances also in powers of 

 discrimination ; it learns to distinguish that which is essential from that 

 which is accidental, it becomes capable of abstractions, and it reasons 

 upon phsenomena divested of any connexion with matter : it observes and 

 remembers what are the invariable points of analogy, and it rejects all 

 others. Each step in knowledge enables it to diminish the number of ap- 

 parent laws, and to discover that many effects at first sight dissimilar 

 depend upon an identical cause. 



It has accordingly been found that the greater our knowledge of facts, 

 the simpler and more limited are found to be the laws to a knowledge of 

 which they lead. 



There is something exquisitely beautiful, highly pleasurable to the mind, 

 in the approximations which are thus daily becoming evident, towards the 

 determination of all phsenomena into a dependence upon a very limited 

 number of laws, or it may be upon a single one ; a genera! physical law to 

 which all effects whatsoever may be referred, of which those which we now 

 regard as laws are only modifications, and into which they are all finally 

 resoluble — a law potent through the boundless regions of space, unaffected 

 by the lapse of time, and bearing the impress of its omnipotent and un- 

 changeable Author. What a prospect of unity and simplicity does this 

 unfold to the mind, what an evidence of power, what a pledge of con- 

 tinuance ! 



By the connexion then of the physical sciences is here meant the 

 indications of uniformity, or it may be of identity, in the laws to which 

 those sciences are subjected. 



But there is a secondary and unavowed sense, in which the term "con- 

 nexion" is employed in this volume — that of subserviency. Thus it is 

 required to estimate the velocity of lightning, a problem in electrical 

 science. To compass this, mechanics are brought into play, and a wheel, 

 to which a mirror has been affixed, is made to whirl upon its axis. But it 

 is necessary to count the number of revolutions performed by this wheel in 

 a given time. To do this, a third science, acoustics, is called upon, and a 

 peg fastened to the axis is tnade to strike a cord ; and since each tone is 

 known to be compounded of a definite number of vibrations, the velocity 

 of the wheel is readily estimable. This cannot, however, justly be cited 

 as a connexion between the sciences of electricity, mechanics, and acous- 

 tics, but only as an illustration, and a very beautiful one, of the degree 

 in which one science maybe made subservient to the acquisition of another, 

 just as a knowledge of languages is of use in the acquisition of history. 



