TEANSACTIONS OF SECTION B. 599 



4. The Essential Oils : a Study in Optical Chemistry. 

 By Dr. J. H. Gladstone, F.E.S. 



5. An Apparatus for maintaining Constant Temperatures iip to 500°. 

 By G. H. Bailey, B.Sc, Ph.B. 



The apparatus consists of a tube of hard glass, 25 cm. long and 4 cm. in 

 diameter, placed horizontally over a furnace of 6 Bunseu burners, and enclosing 

 a smaller tube in which substances may be heated. Alongside this is the bulb of 

 an air-thermometer, which connects with a U-tube containing mercury. On heat- 

 ing, the mercm'y column is of course depressed in the near limb of the U-tube, and 

 rises in the further limb, the amount of the depression being indicated by a 

 millimeti-e scale. The instrument is first graduated by placing a high boiling 

 thermometer in the heating tube, and then constructing from the readings a curve, 

 by reference to which the temperature may be ascertained when the reading on the 

 scale is known. 



The gas supply passes through a tube fitting into the further limb of the U-tube 

 arranged as a gas regulator, so that, as the mercury rises in this limb, it cuts down 

 the supply. By raising or depressing this regulator the point at which the supply 

 is cut off "is determined, and any desired temperature can thus be maintained in the 

 heating tube. The apparatus has been foimd reliable up to 500°, and it is possible 

 to measure the temperatiu'e with great accui-acy, and to keep it constant within at 

 most 5° with the greatest ease. The author suggests its use for determining the 

 temperature of decomposition of salts, melting-points, and for investigations in 

 dynamical chemistry. 



6. On a neiv Apparatus for readily determining the Calorimetric Vahie of 

 Fuel or Organic Compounds hy Birect Combustion in Oxygen. By 

 William Thomson, F.B.8.E. 



This consists of an arrangement by which the organic substance is burned in a 

 small platinum crucible, set in a non-conducting cup or holder, the whole being 

 enclosed by a thin glass inverted test-tube, and the combustion performed under 

 water. The stream of oxygen is directed on to the burning material by a movable 

 narrow brass tube, so that the combustion is absolutely under control. By this 

 means plumbago or anthracite may be easily and perfectly burned, which cannot be 

 done by the apparatus devised by Mr. Lewis Thompson, which consists in burning 

 the material by means of a mixture of chlorate and nitrate of potash. This last 

 arrangement gives inaccurate results and is unscientific, inasmuch as there are 

 many things which modify the results which cannot be measured, and which vary 

 in each experiment. 



The gases from the combustion in oxygen pass through water contained in a long 

 thin glass beaker ; the glass, platinum, mercury, and brass work used in the 

 apparatus is weighed, and from theii' specific heat their equivalent in water is 

 calcidated — 2,000 grammes of water are used for 1 gramme fuel. 



7. On some Becompositions of Benzoic Acid. By Professor Odling, F.E.S. 



8. The Crystalline Strticture of Iron Meteorites. By Dr. O. W. Huntington. 



The object of this paper was to show that the true iron meteorites have a 

 common crystalline structure, varying only in details, and not in general character.. 



In the first place it is shown that the Widmanstiittiau figures and the Neumann 

 lines are simply the effects of the segregation of impurities durmg the process of 

 crystallisation parallel to the planes of crystalline growth, and are phenomena 

 similar in all respects to those observed in the crystals of many minerals. 



It appears that the Widmanstattian figures, though presenting additional 



