Difference between spectrography and spectrograph
Definitions
noun
- a spectroscope by which spectra can be photographed
- a photographic record of a spectrum
Examples
The air looked sweet and noncarcinogenic on the spectrograph.
How'bout I think about it over a particle spectrograph and call you back?
So presumably the amount present can be deduced from spectrographic data and the amount infered by this and other means is insufficient for the job.