80 G. C. KAROP ON WHAT WAS THE AMICIAN TEST ? 



Harting, " Das Mikroskop," First German edit., p. 288, says : 

 " Mohl particularly recommends the wing scales of ? Hipparchia 

 janira as a test, which he got to know from Amici." Although 

 Harting gives some information about diatoms as tests, and a 

 good deal about Amici and his instruments, there is no mention 

 of any specific " Amician test," a somewhat curious and rather 

 suspicious omission in a work which I regard as by far the best of 

 its day on the microscope. I say suspicious, for I am of opinion 

 that the test called Amician, one particular diatom as understood 

 later, was something got up, so to speak, for the English amateur 

 at a time when there prevailed a kind of mania here for increased 

 apertures solely for resolving the markings on certain diatoms, 

 which was quite without parallel on the continent, I fully 

 recognize the value of the diatom and its reaction on the wealthy 

 dilettante ; between them they are in great measure answerable 

 for the modern microscope and its magnificent objectives ; but the 

 early continental worker who employed the microscope as any 

 other tool, came to regard the Englishman's proceedings as childish 

 trifling, and looked upon his great, shining, complicated stand 

 with its wonderful accessory apparatus merely as " an expensive 

 peepshow," while he was quite indifferent to the sempiternal 

 checks, dots, lines and little else so painfully evolved by it. An 

 " Amician test," apparently, was not for him. 



Be this as it may, however, the question for us is, which was 

 the particular diatom considered to be the Amician test par 

 excellence? A large number, perhaps the majority, of authorities 

 believe it to be Navicula rhomboides. This is first figured, 

 naturally in outline only, in Ehrenberg's "America," 1843, 

 according to Kiitzing, who copies it in his " Bacillarien." W. 

 Smith records it in 1849, but it is doubtful if any lens of that 

 date could have really resolved it, unless it chanced to be a very 

 coarse-lined variety. Mr. Ingpen informs me that he possesses a 

 slide of rhomboides thirty-five to forty years old, by C. M. Topping, 

 the best mounter of his day, labelled simply " Amician Test," and 

 Mr. T. Powell has kindly sent me a similar slide and also so 

 named. On examination it appears to have been mounted as 

 gathered, without any preliminary treatment with acids, between 

 two thin covers, but from lapse of time it has almost perished, and 

 the diatoms, chiefly a very small variety of rhomboides, are quite 

 unresolvable by any optical means in my possession. 



