fraiiu' ol' W(!oil niul aslu'stos is I'asteiitd liinily to ihc coiipcr A liy ropper 

 screws, whifli. liowovor, must not reach tln'oiiuh the wood B. In the 

 center of (he woud and asliestos scinarcs is a circ iilar opriunu- 1), 12 mm. in 

 diameter, to allow the li.iiht retleeted throngh the sta,u"e of the microscope 

 to pass thron.uh the slide. Throntih the side of the wood frame away from 

 the pillar of the luicroscoiu'. as the lu;ilin.i:' sl;;u',' lies in the proiuT posi- 

 tion on the stage of the mieroseope for observation, are two holes for 

 centigrade thermometers. E and K'. The tt'mperatnre at E may be a 

 little less than at E'. and if this is the eas(>. then an average of the tem- 

 peratnres shown by tlM> thermometers ai E and E' shonld lie reckoned. 

 It shonld be aseeriained before tlie exp riment that the two thermom- 

 eters read the same at the same temiieratnre. As they i)ro.iect directl}' 

 in front <lnring eorri'i-t observation, the Ienii;ei;itnre of both is easily seen 

 while (experimenting. Since it is no; al'.vays possil)le or convenient to 

 eariy on rxpt rimrn'.s witli the eepper plat'' of tlie heating stage directed 

 to tlu> riglit as wonld necessarily be tlie ca.so with the th.ermometers on 

 the side shown in I'lgiwe 1. another ari;;iig( nient was resorted to. On the 

 side of the wood frame opposite E and E' are two similar lioles for 

 thernu)meters. F and F\ which allows observation while the copper plate 

 of the luxating stage is tnrnei! to the left or the reverse position to the 

 one in whii-h E and E' eoidd be nsed. It will lie seen from the lower 

 view of the heating stage shown in Fignre 1 that the bnlbs of the ther- 

 uutmeters rest against the copper plate inside the asbestos square C, and 

 in this way the heat is readily conveyed to them. One thermometer only 

 might be nstnl. but tlu> nse of two is more aci-urate and therefore advisa- 

 bl(>. A third position for the heating st.igc is possil)le and for various 

 reasons smnetimes advisable, in which tlie copper plate A is directed 

 away from the oliscrxiM- instead of fnnii the left ov right. Or it may be 

 tnnied aboet on the stage of the microscope throngh an angle of some- 

 what more than lSi»"" and still be capabl(> of perfect nse at every point. 

 It is held to the stage of the microscope by means of iron elamps. the 

 niiper screw of which is provided on its lower end with a small wooden 

 block covered with aslustos. This is nei-<'ssary since a careless disjegard 

 or misnse of snbtancts that are not \iv.ov conductors of heat may readily 

 result in injury to the mit-roscopi'. Heat may be supplied by a gas or 

 alcohol lamp or other source placed undei- A at (! and the thime increased 

 or moved toward C as is desired. 



