He worked in the fields of spectroscopy , atmospheric physics and meteorology . In the field of spectroscopy he found the shift of spectral lines under pressure . In atmospheric physics he found a very good model for the stratosphere in 1909 . He wrote numerous books , including a textbook titled '' Physics of the Air '' , first published in 1920 and considered a standard work of the time , though it was last published in 1940 . He also held some teaching positions at universities . He concluded that the 1815 eruption of Mount Tambora was responsible for the subsequent cooling known as the Year Without a Summer
Year Without a Summer
Year Without a Summer
William Jackson Humphreys