In Fig. 4 a machine is represented in which the field is external to the armature. [Illustration: Fig. 4.] In Fig. 5 we have a thermo-magnetic generator, which corresponds to the disk machine in dynamos. Similar parts are indicated by the same letters in each of these figures, so that no further detailed description is necessary. [Illustration: Fig. 5.] In another modification M. Menges proposes to rotate the burners and leave the armature and distributor at rest. But in this case it is evident that the E.M.F. produced would be much less, because the magnetization of the core would only undergo a variation of intensity, and would nowhere be reversed, except, perhaps, just in front of the poles. In machines modeled on the Brush type it is evident that the distributor need not be continuous. Enough has, however, been said to indicate the extent of the field upon which the principle may be applied.--_The Electrician._ * * * * * OBSERVATIONS ON ATMOSPHERIC ELECTRICITY.[1] [Footnote 1: Abstract of a paper read before the British Association meeting at Manchester, September, 1887.] BY PROF. L. WEBER. I will try to give a short report of some experiments I have made during the last year in regard to atmospheric electricity. It was formerly uncertain whether the electrostatic potential would increase by rising from the surface of the earth to more elevated region of the atmosphere or not, and also whether the potential in a normal--that is, cloudless--state of the atmosphere was always positive or sometimes negative. Sir William Thomson found by exact methods of measuring that the increase of the potential with elevation is very important, and values about 100 volts per meter. That fact is proved by many other observers, especially lately by Mr. F. Exner, at Vienna, who found an increase of 60 to 600 volts per meter. The observations were made by means of an electrometer. In respect of many inconveniences which are connected with the use of an electrometer, I have tried the measurements with a very sensitive galvanometer. In this case it is necessary to apply a separating air exhaust apparatus, for example flame, or a system of points at the upper end of the conductor, which is elevated in the atmosphere. In order to get a constant apparatus, I have used 400 of the finest needles inserted in a metallic ribbon. This system I have raised in the air by means of a captive balloon, or by a kite, which was attached to a conductor of twine or to a twisted line of the finest steel wire. In this way I have attained a height of 100 to 300 meters. When the lower end of the kite line was communicating with the galvanometer whose other terminal was in contact with the earth, a current passed through the galvanometer. For determining the strength of this current I proposed to called a micro-ampere the 10^{-9} part of an ampere. At the height of about 100 meters in the average the current