OCTOBliR. 1911. 



KNOWLEDGE. 



375 



heights 



Ha\ing thus indicated 

 the manner in which 

 instruments ha\'e been and 

 are carried to various 

 IS, a few details 

 concerning them will he 

 ap[)ropriate before discus- 

 sing tht results obtained. 



Glaisher. in Coxwell's 

 "Mammoth."" devoted him- 

 self mainh- to the relation 

 of height with temperature, 

 and with h\-grometric con- 

 ditions, while not overlook- 

 ing possible chemical and 

 magnetic changes, cloud 

 forms, changes of air cur- 

 rents, and so on. His out- 

 fit included a mcrcur\' 

 barometer, aneroid, drv and 

 wet bulb and maximum and 

 mini m u m thermometers. 

 Daniells and Regnaults 

 hygrometers, horizontal 

 magnet, electrometer and 

 sealed exhausted tubes. 

 This appalling array for a 

 single obser\er \\as set out 

 upon a hoard, readv in 

 case of danger to be in- 

 stantly packed for safety. 

 Coxwell acted as time- 

 keeper as well as pilot. 

 Each high ascent cost £^50. 

 so that the number avail- 

 able from the British 

 .Association grants was 

 limited. 



In recent \'ears. of course, 

 self-recording instruments 

 have done the work, those 

 intended for kites being 

 the more solid in form. 

 Yet even the complete set 

 now usualK' attached to 

 these Weighs onl\- one-and- 

 a-half to two-and-a-half 

 pounds, including a clock 

 with recording drum, a 

 large double .\neroid or 

 Bourdon tube barometer. 

 Bourdon tube thermome- 

 ter,* Robinson anemome- 

 ter, and hair h\grometer. 

 This and the thermometer 

 are cased in a polished 

 aluminium ventilation tube. 

 having a vane to keep it 

 end on to the wind. This 

 is most essential to ensure 



liy ://. 



Temperatures and Pressures in a block of Atmosphere 



fifteen miles thick, over a portion of the British Isles, 



July 27th and 29th. 1908. 



Bourdon tubes are circular arcs, tlic 



Uibe exhausted for barometer, and filled with 

 Varying pressure alters the curve. 



true temperature and 

 humidity records. Un- 

 fortunately, Glaisher"s re- 

 sults were to some extent 

 vitiated from ignorance in 

 his time of the necessity 

 for this. In England, now, 

 the much lighter apparatus 

 designed by Mr. Dines is 

 used ; essentially a card- 

 board disc, revolved b\' 

 clockwork. On one side 

 of its upper face is recorded 

 pressure and huinidit\ : 

 on the other temperature 

 and wind speed. 



Eor ballons sondes still 

 lighter apparatus is re- 

 quired. Out of England 

 the usual instruments 

 weigh about one-and-a- 

 quarter pounds. The Ger- 

 man form, perfected In- 

 .Assman, consists of an 

 endless sheet between two 

 drums. One of these is 

 turned by aneroid changes. 

 Two pens pressed against 

 the sheet are mo\'ed at 

 right angles to this motion 

 by changes of temperature 

 and humidit\' respectiveh', 

 being attached to the neces- 

 sary instruments. Time 

 may also, however, be 

 recorded b\- a small clock, 

 though this is not essential, 

 and the whole is encased. 



In England, again, the 

 far lighter Dines" instru- 

 ment prevails, weighing 

 either t h r ee - a n d - a - h a 1 f 

 ounces or one ounce. 

 This, however. discards 

 luiiniditv records. The 

 aneroid is attached b\- one 

 face to the frame, by the 

 other. indirectK-, to a 

 parallel rod of invar, a 

 lever from which moves a 

 st\ lus across the face of 

 a silvered metallic strip, 

 which is attached to the 

 frame. The invar rod is 

 itself part of the metallic 

 thermometer, so that at 

 constant temperature its 

 st}-le makes a parallel 

 scratch, which, however, 

 diverges with a fall of 



a suitable liquid for thermometer 



