Natural philosopher Edmond Halley’s 1686 map of the world winds is emblematic of a new scientific predicament that emerged in the mid-seventeenth century: how to coordinate, compile, and integrate the contributions of many different observers, scattered over time and space. Individual savants who routinely repeated their own observations of stellar positions or plant genera or human bronchia were confronted with the same dilemma: How to synthesize many views of the same object, each differing slightly or strikingly from the others, into a single observation? One solution was to edit numerous observations from hither and yon into a “synopsis,” verbal or visual, as Halley did with the reports of mariners and travelers in his map. Another, often used in botany, was to try to calibrate the senses of the multiple observers beforehand, so as to standardize assessments of color, texture, taste, and smell. Still another, increasingly frequent in astronomy, averaged the values of divergent observations of the same celestial object. All these techniques of collective observation posed problems of ontology and social organization: a general object had to be consolidated out of multiple observations; authority had to be exercised to consolidate a collective out of multiple observers. New kinds of visualization and community made collective empiricism possible.