Missing log entries

Your assumption is correct, I was logging to the default facility. When I changed it to local0, I got similar but not identical behavior. I tried several different facilities and levels, and the results are the same. If I put a timing loop in front of the log statement, I get all my log statements. I found that variable Y must increase as the limit for variable X is increased. For example, I consistently get all 300 lines if I have a 12 count loop in between each log statement

  for {set x 0}{$x<300}{incr x}{
    for {set y 0}{$y<12}{incr y} { }
    log local0 "Number $x"
  }

But if I need 1000 of them, the delay loop needs to be much longer:

  for {set x 0}{$x<1000}{incr x}{
    for {set y 0}{$y<100}{incr y} { }
    log local0. "Number $x"
  }

It appears to me that syslog is getting overloaded.