1) I was sitting on my back patio looking up at a white cumulus cloud that was passing in front of the sun at !0,000 feet and south of my position.2) I saw a perfectly round object move from left to right that looked like a shadow moving between the cloud and sun. I saw the second object because I was still trying to figure out what the first one was and where it went.3) At first, I thought it was a bird, but I couldn't figure out what bird would have a perfectly round shape and move/glide like that. Then I thought it might be a plane but there was no sound. About 20 seconds later, I saw another object that looked and moved like the first one. In between sightings of the 2 objects i noticed a silver large passenger plane at 30,000 feet moving north to south far up to the right of the cloud in an area where there were no clouds.4) The object looked like a perfectly round shadow moving quickly from left(southeast) to right(southwest) between the cumulus cloud and the sun. It made no noise and vanished/ blended in with the sky after it exited the cloud. Since the object puzzled me so, I continued looking at the sky and cloud and about 30 seconds later, I saw another object that had the same shape and moved in the same direction as the first one. When that object passed from behind the cloud it also became invisible/blended with the sky. Both objects were not visible to my eye before entering the cloud as well. They moved at the same height and speed and in a straight path.5) After seeing the first object and expecting to see a bird or plane emerge from the cloud and not seeing anything, I was stunned. I kept saying "what?", "what?" out loud because I couldn't understand what I had seen. This is why I kept looking at the cloud. I didn't move from my chair. Then after 20 seconds, the same object appeared again and I decided that I had try to comprehend what I was seeing. When NOTHING appeared again after the object left the cloud I stood up out of my chair and looked at the sky more closely It was totally invisible. I looked at my watch to make sure that I remembered the exact time it happened. I thought I just saw 2 UFOs and didn't know what to do. I came inside and told my 22 year old son and my 20 year old daughter what I saw. I can't get the vision of those 2 objects moving behind the cloud out of my head! I thought of calling the FAA, Philadelphia International airport and even our local news but I was afraid of ridicule. I posted a question if any of my local friends on Facebook might have been looking at that cloud at that time, but nobody did. I hope that someone else saw them to confirm what I saw.6) They disappeared/were invisible.