86 REPORT—1840. 
the cistern; the vernier has a proper motion upon the scale, 
in order to read off the height*. 
133. M. Kupffer has proposed a stationary barometer, in 
which a siphon-tube stands alone, and quite detached from a 
graduated column, along which a micrometer travels, and reads 
off the differences of elevation of the two extremities of the 
mercuryt.. M. Breithaupt has also proposed a plan somewhat 
similar. It may very safely be affirmed, that the mechanical 
act of reading off the length of the column is already accom- 
plished with more accuracy than the otherwise imperfect nature 
of the instrument requires. 
134. Mr. Daniell recommends Newman’s portable barome- 
ters, with correction for the capacity of the cistern, and such 
have been supplied to the Antarctic expedition§. Mr. Newman 
has adapted an ingenious cast-iron cistern to his instrument, 
which consists of two parts, one of which contains the super- 
fluous mercury during carriage, the other being always full |]. 
135. M. Bunten,of Paris, a most ingenious and excellent artist, 
has made a great improvement on Gay-Lussac’s portable siphon- 
barometer, in which a chamber is left in the principal tube, in 
which any air which may have accidentally left the bend of the 
siphon is inevitably lodged, and may be expelled at leisure 
without injury to the vacuum. M. Bunten constructs these 
instruments himself with peculiar skill, and provides them with 
excellent portable wooden cases. The same artist has recently 
contrived a very ingenious, elegant, and simple cistern-baro- 
meter, with the graduation on the glass, and which can be made 
at so moderate a price as ought to supersede the rude instru- 
ments commonly purchased at twice the cost]. 
136. Greiner, of Berlin, a most excellent manufacturer of 
meteorological instruments of the most delicate kind, has con- 
structed a siphon-barometer, with the material advantage of 
confining the superfluous mercury (which by frequent shaking 
becomes oxidated), and yet in such a way, that the expansion 
by heat cannot possibly endanger the instrument**. His baro- 
meter, more cumbrous and more expensive than Bunten’s, is 
well adapted for nice observations, to be pursued for some time 
at a fixed station, whither the instrument has first to be con- 
veyed. ‘ 
* See Mr. Baily’s description, Phil. Mag., Third Series, xii. 204. 
+ Poggendorff, xxvi. 446. $ Ibid., xxxiv. 30. 
§ Royal Society, Instructions, p. 56. {| Brit. Assoc., 3rd Report, p. 417. 
4 The defect of this instrument in its present form, is the difficulty of access 
of the air to the cistern. 
** There is a descriptive pamphlet published at Berlin in 1835, 
