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• Today we see weather balloons on occasion, but passenger balloons are very rare.

• Every now and then, the blade may strike a bump, breaking loose fragments of ...

• The computer itself blunders (every) now and then.

• For 600,000 years rhyolitic lava erupted on the Yellowstone Plateau intermittently.

• At times (or From time to time), the basin water is shock treated.

• Evaporate to dryness, turning the granules occasionally to insure uniform coverage.