SCIENTIFIC SUMMA11T. 
441 
“ Preussisclier Zeitschr/f. Berg. Huetten u. Salinenwesen,” 1870, p. 145, 
will be found an extremely interesting* paper by Dr. Kosmann, in which 
he gives the results of a comparison between the effects and relative 
■economy of puddling in the ordinary manner, and when done by Siemens’ 
regenerative gas puddling furnace ; although short, the space at command 
will only allow of our giving the conclusions arrived at, which are (1), that 
the Siemens’ furnace is to be preferred in all cases where an extremely high 
heat is required, and where the fuel is of bad quality and unsuited for 
producing sufficient heat when consumed in the ordinary way ; (2) when- 
ever a fixed temperature or a certain quality of flame is required for any 
length of time ; (3) when no use of the waste heat of the flame (as for 
heating steam boilers to drive machinery) is required. And, in addition, 
there is less waste and also somewhat less loss of iron in the slag with the 
Siemens than with the ordinary furnace, as may be seen by a comparison of 
the chemical analysis of the respective slags. 
Silica . 
Alumina 
Protoxide of Iron . 
do. Manganese 
Lime . 
Magnesia 
Soda and Potash . 
Phosphoric Acid . 
Sulphur 
Ordinary furnace Siemens furnace 
. 11*98 15*36 
. 1*H 1*18 
. 68*69 66*33 
. 1*00 0*92 
. 1*79 2*51 
. 0*24 0*92 
. 2*13 0*72 
. 14*43 14*28 
. 0*24 0*28 
101*61 102*50 
The amount of phosphorus or sulphur eliminated in the slag is about the 
same in both instances. If, however, the fuel is of good quality, and the 
waste heat is employed for raising steam, then there appears to be little, if 
any, advantage in the employment of the Siemens furnace, which is known 
to be extremely costly, both in original construction and in subsequent 
repairs. 
MICROSCOPY. 
Sacs in the Tibia of a Flea . — A very long and somewhat important paper 
has appeared in the Q.uekett Club a Journal ” for July, on the above 
subject. The function of these sacs, in the author’s opinion, is somewhat 
peculiar. He says that the action of the contractile sac of the upper tarsal 
joint is first, by slow distension, to become filled with air, the membranous 
sac of the tibia simultaneously collapsing. When fully distended, the tarsal 
sac suddenly contracts to about one-fourth its previous diameter, when at 
the same moment the membranous sac of the tibia becomes fully inflated. 
This rhythmical, alternate movement sometimes proceeds, regularly, at the 
rate of two or three pulsations in the minute, but this is not always the 
case, as he has frequently found that it is suspended for longer or shorter 
periods, and in many specimens it is altogether wanting. Believing that 
