Mr. Barlow on the Refracting Telescope. 11 



me to be important advantages ; but there may be others 

 equally important which have escaped me, and over which, 

 had they occurred to my mind, I might probably have been able 

 to exercise some control. 



This impossibility of foreseeing all the bearings of an in- 

 quiry so completely untried as that which forms the subject of 

 this paper, proves the necessity of an extensive series of expe- 

 riments to elicit the most useful results ; but such a series of 

 experiments, particularly under the disadvantage to which I 

 have alluded above, involves too great an expense to be under- 

 taken at the charge of a private individual. At the same 

 time, I must think that an extensive field of practical optics is 

 here opened, which is highly deserving of cultivation. 



ON THOSE BIRDS WHICH EXHIBIT THE TYPICAL PER- 

 FECTION OF THE FAMILY OF ANATID^S. 



By WILLIAM SWAINSON, Esq., F.R.S., L.S., &c., &c. 



A LTHOUGH natural history, from having been formerly 

 ^^pursued with an exclusive reference to specific differences, 

 long merited its popular definition of being a science of ob- 

 servation, the attention now bestowed upon the generalization 

 of facts, gives the hope that this science will soon become one 

 of demonstration. It is to be feared, however, that in this 

 eager desire to develope general laws, we sometimes overlook 

 those means by which such results are to be obtained, that we 

 theorize, as it has been well observed, where we should ana- 

 lyze*, and decide upon the properties of a group, thought to 

 be natural, before we have thoroughly investigated the group 

 itself. The present generation of naturalists, in fact, are as 

 much prone to fall into error from their over-anxiety to gene- 

 ralize, as were those of the Linnsean school, from an exclusive 

 devotion to specific differences, and a total neglect of all the 

 higher objects of the science. This passion for theory, among 

 our own countrymen, dates its origin from the period when 

 naturalists began to study the celebrated Horse Entomolo- 



* ' It is the prevalent error of the day, among the naturalists, to attempt to 

 generalize where they gught to analyze.' Bicbeno, Linn. Tr. xv. p. 489. 



