Question: who devised the law of conservation of energy
[{'answer': 'Julius Robert von Mayer', 'provenance': [{'wikipedia_id': '67088', 'title': 'Conservation of energy', 'start_paragraph_id': 26, 'start_character': 95, 'end_paragraph_id': 26, 'end_character': 118, 'bleu_score': 1.0, 'section': 'Section::::History.:Mechanical equivalent of heat.\n'}]}, {'provenance': [{'wikipedia_id': '67088', 'title': 'Conservation of energy', 'start_paragraph_id': 26, 'start_character': 0, 'end_paragraph_id': 26, 'end_character': 580, 'bleu_score': 0.979054689945215, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9147130719458568723}, 'section': 'Section::::History.:Mechanical equivalent of heat.\n'}]}]