Ree. May 29 
Bonn May 27, 1857 
Dear Doctor ! 
Prora whom shall I purchase a raicroscope ?' From him, who makes- 
the best. What is the best raicroscope ?' That, which in coraparison with 
the others works better than the others«. Nobody will contest the an - 
swer; if one asks: ^^o'se instrriraent produces raore than the others,?" 
Only he can ecive the answer.who has seen the raicroscopes of the raost 
p-rorainent opticians. Prinn-sheira prefers Schick to all others, Thus I 
can put eraphasis on what Prinprheira hiraself says.that he has no prac- 
tical experience with a Nachet - i.e. he does not know the raicroscope 
of Nachet.- Nachet and Schick do not stand cora.parison with each other,. 
even Benicke is ra.uch further than Schick. Pringsheim and 
never properly did a test. No Schick, as far as I have seen, and here 
alone 
in Bonn /are 3» shows the stripes on- Navioula ang:ulata; A Benicke shows 
a little 
thera, but not very well.always / higher than in Schick and Nachet like 
the ensrlish instrura.ents of Ross, Sraith and Beck,Powell & Lenbach, , very 
well |. with Nachet even already at about 38O tiraes na^nif icationr and 
rather poor light, even x^ithout cross-li^rhting; a Benicke raust have 
cross-lißrhting. . The larere field, the wide focal distance, the abundandT 
lißrht are very apr^^eable i^rith the Schick; what srood is it to be a^rrea- 
ble, if I cannot see with it, what other instruraents show T. By the way,, 
Nachet is not one-sided: • he raakes two kinds of ob jectives; such with a 
small field,sraall focal distance and less light,. but x^ith this great 
shaprness of the iraage (the Ober_haufer type) and he raakes (after eng- 
lish and Schick type^ ob jectives with a very large field:,rauch light,, 
which however according to ray opinion,give never as sharp an iraage 
as those of the first kind.. One needs for different purposes both ob - 
jectives- with advantage, and a good optician should soon fabricate 
(jnent 
thera, as did Nachet.. I shall get soon an instr^ frora hinr , which has 
both; one sees x^-ith both the stripes on the Nax/ioiala. I believe, that 
