DUST IN SPIRAL GALAXIES .1.

We have mapped NGC 660 and UGC 3490 at 1300 mu m. It turns out that th e spatial extent of the cold dust is comparable to the optical size of UGC 3490. Combining the new observations with IRAS data we derive a t emperature of approximate to 17K for the coldest dust component; its e mission dominates the wavelength range from 100 to 1300 mu m. A second warm component of approximate to 50K is required to explain the spect ra down to 25 mu m. This decomposition is corroborated by a reinvestig ation of FIR data for M 51 and the Milky Way. In both cases, the energ y distributions peak around 200 mu m confirming our earlier, strongly doubted results on the dust components in spiral galaxies.