FROST— OBSERVATIONS OF THE ECLIPSE. 287 



was unable to see the flash spectrum at the beginning of totality and 

 could see the reversal of but few lines at the end of totality. 



It would also be perfectly feasible to operate the film by a direct 

 connection with a chronograph, controlled by a conical pendulum ; 

 or, if desired, a graduated change in rate of rotation could be given 

 so that a longer exposure would result before totality (say, an 

 exposure of ^Ao second) and a still shorter (say, %o second), thirty 

 seconds before and after the contacts. I sincerely hope that this 

 simple method will be included in the plans for the next eclipse 

 expedition, because with clear weather it practically guarantees good 

 results. 



I may say here that it is unfortunate that better records of the 

 eclipse were not obtained with movie machines. So far as I have 

 learned no first-class picture was obtained. I took pains to notify 

 some of the film companies, explaining how important it was that 

 they should not depend upon their usual short-focus lenses (two to 

 three inches), but that they should use lenses of at least twenty or 

 thirty inches focus. Some commercial operators at Denver were 

 prepared to do this, and dovibtless would have obtained results both 

 instructive and interesting if the weather had permitted. 



Our program also included the photography of the infra-red 

 region of the spectrum, with the use of films stained with dicyanin, 

 in connection with a small concave grating of sixty inches focus, 

 used directly. This was the instrument I had employed at Wades- 

 boro in 19CO. It was operated by Professor S. B. Barrett, but no 

 results in the infra-red could be obtained through the cloud. It 

 might be a question whether there would be ordinarily time enough 

 for sufficient exposure for the infra-red, and probably future plans 

 in this direction should insure an abundant light-power in the spec- 

 troscope. 



In connection with the apparatus arranged by Professor Park- 

 hurst for the photometric study of the corona was a reflecting tele- 

 scope of six inches aperture and sixty inches focus, covered by a 

 15° prism of ultra-violet glass of the same aperture. One of the 

 exposures made with this instrument is shown herewith, as it brings 

 out an interesting point with respect to the large prominence in posi- 

 tion angle 253°, already shown from Professor Barnard's negative 



