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SummaryA survey has been made of the 21 cm line from neutral interstellar hydrogen in the Magellanic Clouds. These are the fu;st observations of this radiation from an extragalactic source.The observations show that neutral hydrogen extends well beyond the easily visible regions of each Cloud, the gas being in each case less concentrated towards the nucleus than are the bright stars. From the total radiation received, the masses of neutral hydrogen are calculated to be 6 X 10 8 and 4 X 10 8 solar masses for the Large and Small Cloud respectively. Since the Small Cloud is believed to contain much less dust, this means that the ratio of gas to dust is very different in the two systems.The measurement of Doppler frequency shifts has yielded extensive new information about radial velocities within the Clouds. The velocity distribution indicates that both Clouds are rotating. Detailed discussion of the velocities has been deferred for subsequent pUblication.

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The 211~212 transition of acetaldehyde at 3195·167 MHz has been observed in emission in SgrB2 with the Parkes 64 m telescope. Comparison of the intensities of the llO~ 111 and 211 ~212 emission lines suggests that both transitions may be inverted.

The 211 +-212 transition of thioformaldehyde (HCHS) has been observed in absorption in the direction of SagittariusB2. For a rest frequency of 3139· 38 MHz the peak absorption occurs at a radial velocity of 60 ± 4 km s -1. The half-width of the absorption profile is equivalent to 20 kms-1 and the column density of HCHS is greater than 10 16 molecules cm -2. Comparison with the 211 +-212 absorption of formaldehyde (HCHO) at 15 GHz allows the relative abundance of the two molecular species to be computed as a function of the rotational excitation temperature. For thermal equilibrium the strength of the 110-111 absorption in SgrB2 by thioformaldehyde predicted from the 211+-212 HCHS observations is considerably greater than the limits set by a number of observers for the 110-111 transition at 1046 MHz.