146 Notices respecting New Books. 
The case m=m’ is an exception, and must be considered sepa- 
rately: the curve is here in all its changes symmetrical about a 
perpendicular to the axis midway between the two centres M, M’. 
The curve in the first instance, i.e. when / is greater than 
(“m+ “m)?=4m, consists of the two ovals B, A about M, 
and the two ovals B’, A’ about M’. As & decreases to 4m, the 
two ovals A, A! gradually increase in magnitude, and at length 
come together, as before, into a figure of eight, AA’; and as k 
continues to diminish, the figure of eight opens out into an hour- 
glass form AA’, which continues increasing in magnitude, and 
degenerating into the form of an oval. The interior ovals B, B! 
approach more and more nearly together, lengthen out in the 
direction perpendicular to the axis, and present to each other a 
more and more flattened portion. The second value, 
k=(v ml — Vm)? 
which in the general case gives a node, in the present case only 
arises when k=O; and there is not then any node, but the 
curve degenerates in a similar manner to what happens for k=0 
in the general case; viz. the oval AA!’ disappears at infinity, 
while the ovals B, B! coalesce together (their outer parts disap- 
pearing at infinity) into a pair of lines coincident with the per- 
pendicular to the axis midway between the two centres. 
2 Stone Buildings, 
May 31, 1857. 
XV. Notices respecting New Books. 
Gasometry, comprising the leading Physical and Chemical Properties 
of Gases. By Roxsert Bunsen, Professor of Chemistry in the 
University of Heidelberg. Translated by Henry E. Roscokr, B.A., 
Ph.D. With Siaty Illustrations. London: Walton and Maberly. 
Hee many years the reputation of Bunsen as a gas analyst has 
been so high, that working chethists generally have felt the 
necessity for a complete collection of the processes, the methods of 
manipulation, and the formule employed by him in his highly im- 
portant and valuable researches. It is for such persons that the 
volume before us is intended. : 
One of the reasons, perhaps, which makes the methods of Bunsen 
more popular than those of Regnault and Reiset is, that they do not 
require the operator to start with so expensive an apparatus. But 
the method of Regnault, especially as regards the convenience of the 
apparatus, has great advantages, the chief fault being that by its use 
large variations in bulk are expressed by small numbers. One of the 
most successful of Bunsen’s pupils* has so far combined the two me- 
* Professor Frankland. 
