and comtruclcd hij Professor Ainici. 309 



through interest and prejudice are so difficult to be discarded. 

 But as all truths require time to subdue the obstinacy of habit 

 and prejudice, a little patience will conduct us to this issue. 

 It required halt" a century before Hadley's most excellent 

 invention had established that empire which aiterwards be- 

 came universal. 



When in 1819 we recommended in the 2d vol. of the Cor- 

 rcspondance, page 387, to our great opticians, to apply their 

 talents to the perfection of reflecting instruments, we were far 

 from hoping that our wishes would be accomplished so soon : 

 a great step has now been gained, and let us hope that others will 

 be made ; for the proverb says, Liventis facile est addere. To 

 prove the trutli of this adage, we shall begin by proposing 

 here a small addition. The coloured glass applietl to tlie 

 cover of the object-glass (fig. 3), can be inverted, but not 

 brought back again. To correct its defect of parallelism, if 

 there should be any, we only have to add on the other side 

 of the cover a little piece of tube such as is seen at A, and 

 then we can apply this cover with its half-glass coloured in 

 the two sides before the object-glass, and by this means return 

 this glass on the same part of the object-glass, either for its 

 verification, or to cori'ect or remove the error which will occur 

 in the observation, if the sides of this glass be neither plane nor 

 parallel. Before we finish this Note, we cannot refrain from 

 making some remark upon the liberal and straightforward man- 

 ner in which M. Amici has publii-hed his new invention here. 

 Many others would have solicited prizes, rewards, patents, 

 or at the least that it sliould receive the honourable mention 

 or favourable report of some academy, or of some board of 

 longitude. M. Amici despises all these practices, the springs 

 of which are so well understood at this time ; he prefers to jiub- 

 lish with frankness and clearness such ideas of his as may be of 

 public utility. We shall finish this note with a quotation from 

 the letter of one of our most celebrated astronomers, whom we 

 liad made acquainted with M. Amici's new instrument, and 

 who replied to us in the terms following: 



" Truly the discovery is important, and I share completely 

 in your admiration. An invention like this, made in England, 

 would have enriched its author*. If there were any means 



* It is pretended that tlic caleidoscope produced this effect for its in- 

 ventor : this instrument nevertiieless is not of such utility as tiic sector of 

 reflection ; yet it is more amusiujT, and therefore, ttc. <Src 



[\Vc believe tiiat the surmises of these learned foreigners respectiup; tlic 

 riches acquired by inventors in lMi{;land arc altogether erroneous; and that 

 those inventions hy whicli the public are so nuidi beneriled, are too fre- 

 quently attended with fircat loss to their projectors and those who engajje 

 in bringing iheni to perfection. — Edituus.] 



of 



