374. oS. M. Schaeberle—Flewure of a Telescope Tube. 
A specimen which was lifted freely by both magnets gave 
a black strongly magnetic powder, reacting with both ferri- 
and ferro-cyanite as well as with sulpheyanite of Sestatehicur 
a red 
horse-shoe but was not influenced by the ies magnet. This 
a a characteristic feektion with sulph- and ferro- -cyanite of 
ssium, but with the idee saat only gave an almost im- 
béscebGbls blue precipitate w was immediately lost in the 
sory due to the great excess of peroxide. 
ecimen extracted from a greenish micaceous schist from 
tafictonats (locality from which martite was first described by 
Spix and Martius) 2 Lenin identical Ai the Itambé rock, 
but not decomposed, was strongly attracted by both magnets 
and gave a black yore ee mage etic powder reacting for both 
per- and prawetde of iron. From a similar rock from Serro, 
magnetic but in different degrees and both gave the reactions 
for the two oxides, but the powder of the first was black and 
of the second red. In another specimen from near Serro, small 
splendent, strongly magnetic crystals, giving a black powder, 
were embedded in compact hematite. In another gent lot of 
brilliant crystals, all were so strongly magnetic as to form them- 
selves in strings of four or five on both magnets. 
In these experiments all possible sradutoge as ‘regards mag- 
netism and composition between typical ion lg and yas 
were found. Specimens from the surface, or from much dec 
osed rock, will naturally be of pure oligiste, but prepeon: no 
external evidence of the change from magnetite unless it be an 
ge most imperceptible dulling of the surface and a slight cappery 
ster. 
Art. XL.—A method for yeas ing the flexure of a Telescope 
Tube for all positions of the Instrument; by J. M. SCHAEBERLE. 
used for this purpose. This maximum flexure is then assum 
to vary as the cosine of ~ altitude. I propose in this paper 
to give a very simple method by means of which the oane 
of this law can be eg directly for all positions of the tu 
nothing but a small A ane mirror, silvered by Draper’s process 
being required for this purpose. To this mirror is cemen 
circular ring of cardboard of just sufficient thickness to sreepitt 
