How did the invention of the spectroscope in 1859 change the science of chemistry

Gustav Kirchhoff and Robert Bunsen built the first spectroscope (1859) and studied the patterns produced by elements vaporized in a Bunsen flame. Using this method of spectrum analysis led to the discovery of cesium/rubidium/thallium. Spectra were soon obtained for the different elements and their lines charted. 

An optical device for producing and observing a spectrum of light or radiation from any source, consisting essentially of a slit through which the radiation passes, a collimating lens, and an Amici prism.

You would do 1500/4 and the answer is 375