In the course of editing this volume I discovered that I am temper- amentally unsuited to the task, an impediment that in no small way accounts for the fact that its publication is later than I would have hoped or anticipated. I am, at heart, a pedant, particularly with respect to the use and abuse of the English language. Many of my scientific colleagues are a good deal less punctilious; they take the reasonable view that if the message is clear, the manner of expression is unimportant. Experience has taught me that what is clear to the author is often quite unclear to the reader unless the author takes the trouble to express himself with precision. I have also found that most scientists are unwilling to devote to the presentation of their results the care that they lavish on obtaining them. But I found myself slipping beyong this often justifiable complaint into a state of inexcusable self-righteousness. It began innocently enough. Conscious of the need for speed, I read the first two or three texts with murmurs of approval, and scribbled 'no changes needed' on the title page of the copy. Then I began to notice one or two grammatical mistakes, plural verbs with singular nouns, mixtures of tenses, and so on, which had to be corrected; not serious, I told myself, a matter only of changing a word here, retyping a line there. Quickly I sank deeper.

Table of Contents:
Physical and Dynamical Conditions in Interstellar Clouds.- Detection of Submillimeter Lines of CO (0.65 mm) and H2O (0.79 mm).- New Detections of Spectral Lines in the Frequency Range 260–285 GHz.- Further Observational Studies of the High Velocity Molecular Source (“Plateau”) in Orion.- High Velocity Gas in the Orion Nebula.- High Spatial Resolution Studies of H13CN, H12CN and HCO+ J= 1?0 Emissions in Orion A.- Lunar Occultation Observations of Millimeter CO Emission in S255.- Radio-Frequency Observations of Interstellar CH4 and HC5N.- On the Identification of Mm-Wavelength U-Lines.- Long Chain Carbon Molecules in the Interstellar Medium.- Long Carbon Chain Molecules in the Laboratory and in Space.- The Relative Distribution of Ammonia and Cyanobutadiyne Emission in Heiles 2 Dust Cloud.- Observations of HC5N (J=12?11 and 13?12) and HC7N (J=28?27), including a Detection of B335.- Spectra of the 10–01 Transition of Sulfur Monoxide in Interstellar Clouds.- CN Observations in Taurus Dark Cloudlets.- C2H and HC3N in Interstellar Clouds.- Detection of New Ammonia Sources.- Ammonia Observations of the Molecular Clouds near S68, S140 and OMC2.- Ammonia Observations of the Molecular Cloud near S106.- The Core of a Quiescent Cloud, L183.- Observations of NH3 toward DR21.- High Resolution 4.8 GHz Mapping of H2CO using the Westerbork Synthesis Radio Telescope.- Surveys of the 4.8 GHz Formaldehyde Absorption Line in Dark Clouds in M17 and NGC 2024.- Cloud-to-Cloud Variations in H2CO-to-H2 Ratios.- Formaldehyde in L1551, L134 and the Galactic Centre.- Observations of the 3.4-mm HCO+ Line toward the Galactic Centre.- CO and OH in the Galactic Center Region.- In Search of ? 5K Galactic Molecular Gas.- CO (J=2?1) Observations of Several Galactic HII Regions.-Molecular Cloud Densities from Observations of Carbon Monosulfide.- CO Observations in the Southern Hemisphere.- CO (J=2?1) Observations of the Carina Nebula and G 333.6-0.2 and a Search for CO in LMC and SMC.- Population Inversion and Suprathermal Excitation in Carbon Monoxide.- 1.0 mm Continuum Observations of Cool Southern Clouds.- The Extinction Efficiency of Dust Grains at 1 Mm.- Comparison of Submillimeter and CO Brightness in Orion and Mon R2.- The Evolution of Giant Molecular Clouds.- The Disruption of the Molecular Cloud Associated with the North America and Pelican Nebulae.- The Structure and Evolution of the W3 Molecular Cloud.- Atomic Hydrogen in and around the Giant Molecular Cloud near W3 and W4.- High Rate of Destruction of Molecular Clouds by Hot Stars.- The Interaction of T-Tauri Stars with Molecular Clouds.- Observations of the J=1?0 and J=2?1 Lines of 12CO in L1551: Evidence for Anisotropic Mass Loss.- Ammonia Observations of Dark Clouds containing Herbig-Haro Objects.- Hydrostatic Models of Molecular Clouds.- Contagious B Star Formation in the Rho Ophiuchi Dark Cloud.- A Nearby Example of a Giant Molecular Cloud.- Cold HI Gas in the Region of the Giant Molecular Cloud near M17.- Search for CO in Atomic Hydrogen Clouds.- Optical and Theoretical Studies of Giant Clouds in Spiral Galaxies.- Molecular Clouds in Orion and Monoceros.- Columbia CO Survey: Molecular Clouds and Spiral Structure.- Molecular Fan of 360-pc Radius in the Galactic Center Region.- The Galactic Rotation Curve to R = 18 kpc.- The Hydrogen Molecule as a Collision Partner.- Recent Laboratory Work on Molecules of Possible Importance for Interstellar Studies.- Far Infrared Laser Magnetic Resonance Spectroscopy.- Optical Observations of Interstellar Molecules.- Observations ofInterstellar Molecules with the International Ultraviolet Explorer.- Interstellar Line Spectra of a Dense Cloud: The VI Cygni Association.- Rotational Fine Structure Lines of Interstellar C2 toward ? Persei.- Laboratory Measurements of Oscillator Strengths of Ultraviolet Molecular Lines of HC1 and H2O and Column Densities of These Molecules in the Zeta Ophiuchi Cloud.- Chlorine Chemistry in Diffuse Interstellar Clouds.- Molecular Formation in Hot Diffuse Clouds.- Formation of Simple Molecules by C+ Reactions on Oxide Grains in Diffuse Clouds.- The Photodissociation of Interstellar CH+.- Charge Exchange and Fine Structure Excitation in O-H+ Collisions.- Molecular Synthesis in Interstellar Clouds: the Radiative Association Reaction H+OH ? H2O+h?.- Experimental Measurements of Ion-Molecule Reactions.- Interstellar Sulfur Chemistry.- An ICR Study of Ion-Molecule Reactions in the C2H2/HCN System.- An ICR Study of an Association Reaction at Low Pressure.- Laboratory Studies of Interstellar Carbon/Nitrogen Ion Chemistry.- Gas Phase Synthesis of Amino-, Cyano- and Nitroso-Compounds in Interstellar Clouds.- The Formation of Complex Interstellar Molecules by Radiative Association.- The Formation of Interstellar Molecules via Radiative Association Reactions.- On the Formation of Interstellar Linear Molecules.- Laboratory and Modeling Studies of Chemistry in Dense Molecular Clouds.- Molecular Evolution in Dense Clouds.- The Determination of Electron Abundances in Interstellar Clouds.- Molecule Formation in Cool, Dense Interstellar Clouds.- Laboratory and Theoretical Results on Interstellar Molecule Production by Grains in Molecular Clouds.- Interstellar Molecules on Dust Mantles.- The Formation of Hydrocarbons and Iron— Hydrides on Cold Interstellar Grains — ExperimentalStudies.- The Chemical Identification of Grain Mantles by Infrared Spectroscopy.- Infrared Molecular Absorption Features.- Reproduction of the Interstellar Ice Band by Grain Mantle Analogs.- Correlations between the ?2200 Feature, the Diffuse ?4430 Band and EB-V.- Correlations for Interstellar Molecules and Diffuse Bands.- Measurements of Isotopic Abundances in Interstellar Clouds.- Isotopic Abundance Ratios from Microwave Observations of Formaldehyde.- Isotope Ratios in Interstellar Formaldehyde.- The 12C/13C Ratio in Interstellar Dark Clouds.- CO Abundance and Isotopic Fractionation in Dark Clouds.- CO Isotope Line Shapes in Dark Clouds.- Isotopic Fractionation in Interstellar Carbon-bearing Molecules Unrelated to Carbon Monoxide.- Interpretation of Isotopic Abundances in Interstellar Clouds.- Detection of Deuterated Formaldehyde in Interstellar Clouds.- Theoretical Considerations of Shock Wave Behavior.- Observations of Shock Waves in Interstellar Clouds.- Observations of the V=0 S(2) Line of Molecular Hydrogen at 12.28 ?m in the Orion Molecular Cloud.- Spectra of the 2.12 µm Quadrupole Line of H2 in the Orion Molecular Cloud.- Molecule Formation in the Seyfert Galaxy NGC 1068.- Molecular Clouds near Supernova Remnants.- Behavior and Significance of Circumstellar Clouds.- Observations of Circumstellar Clouds.- Radio Detection of Ammonia in IRC+10216.- Molecular Abundances in IRC+10216.- Infrared Heterodyne Spectroscopy of Circumstellar Molecules.- Spectroscopic Studies of IRC+10216 and Similar Objects.- Infrared Spectroscopy of Molecules in Circumstellar Material.- Observational Characteristics of Masers Associated with Stars.- VLBI Observations of the V=1 and V=2 SiO Masers in W Hydra and VX Sagittarius.- Vibrationally Excited Silicon Monoxide Masers.- TimeVariation of SiO Maser Emissions.- Time Variability of the Orion A, R Leo and o Ceti SiO (v=1, J=2?1) Masers.- Polarized Emission in the Broad SiO Feature from R Leo.- SiO Emission from the Orion Nebula.- The OH Circumstellar Maser in Late-Type Stars.- Interpretation of Circumstellar Masers.- Pumping Mechanisms of OH Masers.- Observations of Masers in Regions of Star Formation.- Absolute Positions of OH Masers Associated with HII Regions.- The Pumping of Interstellar OH Main Line Masers: an Efficient Mechanism.- ?-Doublet Population Inversion in Collisions of OH, OD, CH, CD and NH+.- Collisional Inversion of the Populations of ?-Doublets in CH and OH: a Critical Study.- Pumping of Strong H2O Cosmic Masers.- Time Variations of Interstellar Water Masers in HII Regions.- Further Observations of the H2O Emission from NGC 4945.- The Interpretation of High Velocity H2O Masers.- Far-Ultraviolet Objective Spectrographs Surveys for Mapping of Interstellar H2, H, and CO.- Future Possibilities for Ultraviolet Observations of Interstellar Molecules.- Maser Amplifiers.- Wideband Spectrometers for Millimetre Wavelengths.- Acousto-Optic Radiospectrometers for Mm-Wave Spectroscopy.- Future Spectral Line Research with the VLA.- New Experimental Possibilities and Future Prospects for 1–5µm Infrared Spectroscopy of Interstellar Molecules.- A 10 Micron Heterodyne Receiver for Ultra High Resolution Astronomical Spectroscopy.- New Experimental Possibilities and the Future at Far IR Wavelengths.- Detection of Interstellar BS in the Cirrus Dark Cloud of the Numbbum Association I — An Intuitive Model and Its Subsequent Observation.- Author Index.- Index of Astronomical Objects.- Molecules Index.