Effect of gravitational lenses on the microwave background, and 1146 + 111B,C

We suggest a simple check of the proposal by Turner et al.1 that the pair of quasars 1146 + 111B,C are, in fact, two images of the same object lensed by an intervening object. If the lens is a cluster, either of normal galaxies or of dark matter, the microwave background seen through the cluster will be distorted by the Zeldovich-Sunyaev effect at the 10−3 level.