The phrase "by intervals" is correct and usable in written English.
It can be used to describe actions or occurrences that happen at regular or irregular intervals of time or space.
Example: "The train arrives by intervals, making it difficult to plan our journey."
Alternatives: "at intervals" or "in intervals."
As expected, China and Russia have lagged behind by intervals that are ten times larger than the norm.
In some cases there are several great waves separated by intervals of several minutes or more.
Given that the history of Al Qaeda tells us that its major attacks are separated by intervals of 12 to 24 months, we'll find out soon enough.
Our eyes, presented with a series of still images separated by intervals of darkness, like movie frames or pages of a flip book, will perceive motion.
"That all men sleep by intervals" required no further elaboration from John Locke, who did much of his sleeping during the latter part of the seventeenth century.
The cities of Bundaberg, Rockhampton, Mackay, Townsville, and Cairns are separated by intervals averaging more than 200 miles (320 km).
The interactions are punctuated by intervals, sometimes only a few seconds long, of rest, solitude and reflection.
Since major Qaeda attacks are planned well in advance and have historically been separated by intervals of 12 to 24 months, we will find out how much we've been distracted soon enough.
At the same time he finished a filmed interview, broken by intervals of abstract color and light, with the civil liberties lawyer Lynne Stewart, who was convicted of passing information from an imprisoned client, Sheik Omar Abdel Rahman, to terrorists.
The storm's wide bands brought drenching rain but were separated by intervals of dry air and sunshine, leaving hours of calm weather.
While the latter is, indeed, called upon to sustain the interest of an audience for three acts, these acts are broken up by intervals during which the audience can relax.
