“Algy” refers irreverently to Algernon Charles Swinburne, English pre-Raphaelite poet, whose poem “The Triumph of Time” contains the lines:

I will go back to the great sweet mother,
Mother and lover of men, the sea.

So Buck is slightly misquoting, probably on purpose. (He quotes the line accurately later in the passage.)

Actual serious painting of Swinburne by William Bell Scott

Modern science basically seems to bear this out. One 1993 study concluded that while “pain is rare in dreams,” it’s “nevertheless compatible with the representational code of dreaming.” In the study, though, the “references” to pain “appeared to be direct, untransformed incorporations of real sensations produced by stimulation” — in other words, only when scientists gave sleeping subjects the laboratory equivalent of a bruise from the bedstead did pain enter into their dreams.

Before electric streetlamps came along, gas lamps were the standard. Now those that remain are preserved purely for nostalgia purposes, and even many of these are being phased out for environmental reasons.

http://youtu.be/6Hgk7CY4RGY?t=39s

According to the Environmental Protection Agency website:

The objective of FIFRA is to provide federal control of pesticide distribution, sale, and use. All pesticides used in the United States must be registered (licensed) by EPA. Registration assures that pesticides will be properly labeled and that, if used in accordance with specifications, they will not cause unreasonable harm to the environment. Use of each registered pesticide must be consistent with use directions contained on the label or labeling.

Oh, Bern. BERN.

Bern is the “federal city” or de facto capital of Switzerland. Remember the Bern disaster scenario from the original SimCity? The city was struggling with a horrible, horrible plague of—traffic congestion. Sleepiest disaster ever.

http://youtu.be/i4kEduf5JpU?t=40s

Auden may be slyly ruminating on unrequited human love as well as our unrequited love for the natural world.

i.e., like a devil’s face that sin has made ugly and sickly-looking.

thorough bass
A. Also called basso continuo (Music / Classical Music) (esp during the baroque period) a bass part underlying a piece of concerted music. It is played on a keyboard instrument, usually supported by a cello, viola da gamba, etc.
b. (as modifier) a thorough-bass part

Musical study was among the fairly narrow set of activities considered proper for young ladies at the time.

This verse and verses 28-29 below indicate that man is to be the steward of the earth; he is to bring the material world and all of its varied elements into the service and good of mankind, and he is to do so with understanding. He is to care for, tend to, and use the animals to their fullest potential in a just manner.