NEW LIMIT ON THE RATE-DENSITY OF EVAPORATING BLACK-HOLES

Data taken with the CYGNUS detector between 1989 September and 1993 Ja nuary have been used to search for 1 s bursts of ultrahigh-energy gamm a rays from point sources at arbitrary locations in the northern sky. We find no evidence for such bursts. We set a theory-dependent upper l imit on the rate-density of evaporating black holes of 8.5 x 10(5) pc- 3 yr-1 at the 99% C.L. When the same emission spectrum is used to reca lculate previous upper limits based on direct searches, this limit is the most restrictive by nearly 2 orders of magnitude.