TROWBRIDGE. — HIGH ELECTROMOTIVE F< 'RCE. 'J 1 
I have not been able to produce the new series of hydrogen lin < discovered by 
Professor E. C. Pickering in the spectrum of certain stars. 
2. The limit of strength of current and electromotive force that one ran employ 
in the study of gaseous spectra of rarefied gases is far below the safety limit of tin- 
glass or quartz tube which is employed, for the containing v< el contribute* many 
impurities which come into strong evidence with powerful discharges; moreover, the 
resulting continuous spectrum completely masks the line spec tram. 
3. It seems probable that many of the lines in gaseous spectra are composite lines, 
especially those which are seen with condenser discharges. The so-called four-line 
spectrum of hydrogen is enhanced by the presence of water-vapor. 
4. A characteristic spectrum common to rarefied oxygen, hydrogen, and nitrogen, 
is obtained in glass tubes and quartz tubes when the limit of safely of the tubes is 
approached. (Fig. 11, Plate XXVII.) 
5. The red line of hydrogen, 6562.10, can be reversed in a tube fill* 1 with rarefied 
hydrogen. 
6. In general it is difficult to determine whether one has succeeded in reversing 
gaseous lines in the case of powerful discharges through rarefied gases on account 
of the continuous spectrum which occurs. 
7. Metallic spectra obtained in capillary tubes filled with rarefied air are character- 
ized by a reversal of most of the strong lines, with a pronounced broadening or Hare 
toward the red end of the spectrum. This phenomenon occurs with powerful con- 
denser discharges. 
8. Powerful electric discharges in air resulting from the discharge of many con- 
£^o »*. ««.* - — 
densers in series exhibit at each fork or angle of the discharge brush discharges 
characteristic of the positive pole; and also an explosive effect. 
9. Beyond 3,000,000 volts the leakage and inductive effects inside a building pre- 
vent even approximate measurements of relation of length of discharge to voltage. 
10. The new construction of the large storage battery described in this memoir 
will, I believe, greatly add to its life and usefulness; for the battery can be hort- 
circuited without fear of injury. The lead plates in the first form of battery were 
renewed once in twelve years. A battery of 20,000 cells forms a unique installation 
for a physical laboratory, and contains the promise of great usefulne,^ , especially in 
cases where uniform and steady electric fields are necessary. 
Jefferson Physical Laboratory, 
Harvard University. 
