"I started writing in the 1930's when I was eighteen years old. And deep inside me I'm still eighteen and it's still 1938."
- Isaac Asimov

You just don’t read this kind of empathy for alien races these days:

“Did the Prostak scientists watch the transcendental spectacle in their powerful telescopes? If so, what joy there must have been in that world, what a waving of tentacles, what a shimmering procession of bright red glyphs across their strange communication disks! How that orange glowing air must have vibrated to emanations of joy and of thankfulness!”

Here's a quote from Gray Lensman (1941) by E.E. 'Doc' Smith:

"Therefore, with every faculty of his newly-enlarged mind concentrated upon the thought-screened, armored head behind the billowing gun and flaring projectors, Kinnison held his line and forged ahead..."

"Attentive as he was to Helmuth's thought-screen, the Patrolman was ready when it weakened slightly and a thought began to seep through, directed at that peculiar ball of force."

Thanks to Alan Willard for contributing the quotes from Gray Lensman.

Here's another gripping quotation from Second Stage Lensman:

"The horrible parasitism went on for ages. The Velantians fought vainly; their crude thought-screens were almost useless until after the coming of the Patrol. Then, with thought-screens that were of real use, and with ships of power and with weapons of might, Worsel himself had taken the lead in the clean-up of Delgon."

Compare to the Tin Foil Hat (Tin Pulpit) from The Tissue-Culture King (1927) by Julian Huxley, which is apparently the original story from which the "tin foil hat" idea is taken. See also the thought shield from Back to 20,000 A.D., by Nat Schachner (w. AL Zagat), published by Wonder Stories in 1931.