Rocket spectroscopy has mapped the solar spectrum from the ground level cut-off near 3000 Å down to the short wavelength limit of the X-ray region. The spectrum has been photographed to 84 Å and scanned photoelectrically to somewhat shorter wavelengths. Throughout most of the ultra-violet the spectrum is known with a resolution of about half an ångström. The profile of Lyman-α has been measured with a resolution of 0·03 Å. In the X-ray region, the spectrum is known only in broad outline from measurements made with narrow-band photometers.Fraunhofer lines disappear near 1500 Å, beyond which chromospheric and coronal emission lines dominate the spectrum. The strongest lines observed are H Lyman-α (1216 Å) and He II Lyman-α (304 Å). In the X-ray region the total flux (1-100 Å) varied by a factor of 7 over the past solar cycle under quiet conditions and exhibited a progressive hardening with increasing solar activity. From sunspot minimum to maximum the flux in a 2-8 Å bandwidth increased several hundred times. At 8-18 Å the increase was a factor of 40 to 60. Solar flares were accompanied by large over-all increases in X-ray flux and especial enhancements of the shorter wavelengths.Solar disk photographs in H Lyman-α and X-rays show that short wavelength emissions are intensified over active regions. In the ultra-violet, the intensity from plage areas averages four times the background brightness. In the X-ray spectrum, active regions may be eighty times as bright as the quiet background. A strong correlation exists between X-ray sources and centimetre wave sources.