We have conducted an extensive optical search for small comets with the cha
racteristics proposed by Frank et nl. [1986] and Frank and Sigwarth [1993,
1997], The observations were made using the 0.5-m reflector of the Iowa Rob
otic Observatory between September 1998 and June 1999. The search technique
consisted of tracking a fixed point in the ecliptic plane at +/-9 degrees
geocentric solar phase angle. The telescope scan-ate was chosen to track mo
ving objects prograde 10(-2) relative to the Earth at a distance of 55,000
km. The camera was multiply shuttered to discriminate against trails caused
by cosmic rays and sensor imperfections. Of 6143 total images, we selected
2713 which were suitable for detection of objects with a magnitude 16.5 or
brighter with 120 pixel trails. The sensitivity and reliability of the vis
ual detection scheme were determined by extensive double-blind tests using
synthetic trails added to over 500 search images. After careful visual insp
ection of all images, we found no trails consistent with small comets. This
result strongly disagrees with previous optical searches of Yeates [1989]
and Frnnk et al, [1990], whose detection rates and magnitudes, when convert
ed to the present search, predict 65 +/- 22 detections. We conclude that at
99% confidence, the number density of any prograde objects in the ecliptic
plane brighter than magnitude 16.5 with speeds near 10 km s(-1) have a num
ber density less than 5% of the small-comet density derived by Frnnk et nl,
[1990]. Any object fainter than this magnitude limit with a mass correspon
ding to the small-comet hypothesis (M > 20,000 kg) must have either an impl
ausibly low geometric albedo (p < 0.01) or a density larger than that of wa
ter.