26 
GLEANINGS IN SCIENCE. 
this opinion the writer in the Government Gazette satisfactorily objected the 
journey of Lieutenants Wilcox and Burlton, in which they visited the Irawadi in 
latitude 27" 31', and found it of so moderate a volume as not to warrant more 
than a comparatively short course from its origin. 91. Klaproth, obliged to admit 
this objection, yet unwilling to abandon his Chinese authorities, turns to one 
of t ho eastern branches of the. Irawadi, which he now thinks must he the Sanpu. 
This new view of the case is set forth in a pamphlet which has been transmitted to 
the Asiatic Society by the author. 
We notice the subject for the purpose of making our readers acquainted with 
the progress of the discussion, and the fact that nothing which has been yet ad vane- 
ed has carried conviction to M. Klaproth's mind. His advantage in being the 
only one engaged in the controversy who has access to the authorities he lays so 
much stress on, is great ; for it may be, that the sharp-sightedness of an opponent 
might detect a flaw in those documents, which is overlooked by the compla- 
cency of the party to whose views they are subservient. 
There are some particulars yet to be brought forward, which willstrengthen con- 
siderably the opinion of our Calcutta Geographers ; and we expect, even occasion 
some degree of scepticism to 91. Klaproth as to the value dfhis Chinese authorities. 
/ 
. 2. Circular Instrument for observing double Altitudes. 
Those of our readers who receive the Transactions of the Astronomical Society 
will remember a plan of a new circle proposed by Holland in the vol. 2d The object 
of it ist o combine the direct and reflected observation of any heavenlv body by means 
of two parallel circles, each furnished with a telescope, and thus prevent the 
possibility of any derangement of the instrument while being moved from the 
direct to the reflected object. It is sufficiently well known that the method of 
observing by reflection which renders us independent of plumb line or level is, par- 
ticularly when thus facilitated, greatly superior to theold one. M erc any authority 
wanting to recommend the instrument, the approbation of the Astronomer Royal 
ought to he sufficient. 
The use of the instrument is obvious. M r hile one telescope and circle is addressed 
to the direct object, the other is employed with the reflected : thus are obtained 2 
readings, multiplied into 8 by 4 verniers' The telescopes being then respectively chan- 
ged, 8 new readings are obtained, making in all 16. By turning it half round 
in azimuth, this number is doubled, so that the errors of division must be greatly 
diminished in a mean of 32 readings*. Such an instrument is particularly adapted 
to Delambre's method of C. 91. altitudes. 
The expectations excited by 91r. Holland’:, description have been fully gratified 
by the sight of one of these instruments, which we had an opportunity of viewing 
about two months ago, the property of Captain Fisher, Surveyor in Sylhet. In 
symmetry of appearance, a feature, ns observed by Troughton, by no means uncon- 
nected with the good performance of an instrument, it is hardly inferior to the 
works of that great artist. The two vertical circles are divided on their edo-es very 
beautifully on silver, and instead of the four verniers proposed in his paper” he has 
given two micrometersf, which subdivide to 2" a severe test, as the maker observes 
of an engine divided instrument : . The horizontal circle is furnished with five ver- 
niers, — a preferable arrangement to six, as in reversing the telescope the verniers do 
not come on the same set of divisions. In verniers which lie on the extremities of 
a diameter, as in the case of 2, 4. 6, 8, & c. reversing the telescope, of course merelv 
occasions them to interchange places, and the measure has therefore no tendenrv 
to reduce the errors of division. un ity 
t Cl UIC1 S . 
» It appears to tis tu.u t 
new readings b- obtained. J “o'- peaces, and no 
t r We doubt if the maker has improved the instrument bv this i 
description he nn-ntions four fixed verniers which antflv to both L \ an S e - In his 
using the Instrument for meridian altitudes in the method practised rt^V 0 tilat ia 
obsen-uui v. there could be no uncertainly in what Mr. Pond calk l£ he . Gre «nw>ch 
independent -^and^ pmlmbili^^Isu^iL' 6 ^.^t^^^easure 
W r ~ -»W preferred 
