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reflecting-plate_n that_o make_v those_o flexure_n the_o three_o and_o fourteen_o figure_n represent_v the_o tube_n shorten_v by_o two_o or_o three_o reflection_n and_o so_o serve_v to_o shorten_v the_o tube_n by_o two_o three_o only_o these_o be_v of_o use_n for_o a_o very_a strong_a eye_n and_o with_o a_o small_a aperture_n of_o the_o object-glass_n and_o when_o the_o sun_n be_v near_o the_o horizon_n or_o its_o light_n be_v a_o little_a diminish_v by_o a_o fog_n thin_a cloud_n or_o the_o like_a if_o it_o be_v think_v more_o convenient_a to_o have_v this_o long_a tube_n to_o lie_v always_o horizontal_n and_o consequent_o that_o there_o shall_v be_v no_o need_n of_o have_v a_o pole_n or_o engine_n to_o raise_v the_o tube_n it_o may_v be_v frame_v somewhat_o like_o that_o in_o the_o four_o figure_n where_o the_o same_o letter_n answer_v to_o all_o the_o part_n abovementioned_a or_o else_o like_a that_o in_o the_o six_o figure_n the_o letter_n of_o both_o which_o be_v the_o same_o 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but_o a_o little_a incline_n so_o as_o the_o reflection_n from_o that_o side_n which_o be_v further_a from_o the_o concave_n may_v be_v cast_v another_o way_n and_o not_o fall_v at_o all_o upon_o the_o three_o reflecting-plate_n â—_o ζ_n and_o because_o the_o wedg-like_a form_n of_o this_o transparent_a plate_n of_o glass_n c_o d_o will_v cause_v a_o refraction_n and_o consequent_o a_o coloration_n of_o the_o ray_n therefore_o there_o must_v be_v another_o wedg-like_a plate_n exact_o as_o may_v be_v like_o the_o former_a which_o at_o some_o distance_n as_o at_z m_z p_o where_o the_o reflection_n will_v not_o come_v to_o fall_v upon_o the_o plate_n â—_o ζ_n must_v be_v so_o fix_v that_o the_o thin_a part_n of_o this_o may_v lie_v just_a upon_o the_o thick_a part_n of_o c_o d_o and_o the_o thick_a of_o this_o over_o the_o thin_a of_o that_o by_o which_o mean_v both_o the_o false_a reflection_n and_o refraction_n will_v be_v remove_v from_o â—_o ζ_n that_o ray_n be_v reflect_v to_o γ_n θ_o and_o from_o γ_n θ_o to_z o_fw-mi the_o focus_n and_o so_o through_o the_o lens_n z_o to_o the_o eye_n x._o this_o i_o take_v to_o be_v the_o best_a by_o reflection_n but_o it_o may_v be_v twenty_o other_o way_n contrive_v which_o i_o shall_v not_o now_o spend_v more_o time_n in_o describe_v it_o be_v so_o easy_a a_o matter_n from_o the_o consideration_n of_o these_o i_o have_v mention_v to_o make_v a_o hundred_o other_o variation_n of_o the_o principle_n to_o this_o helioscope_n may_v be_v fit_v instrument_n for_o measure_v the_o maculae_fw-la faculae_fw-la and_o nebulae_fw-la visible_a in_o the_o body_n of_o the_o sun_n as_o also_o the_o space_n pass_v by_o they_o in_o a_o day_n two_o three_o ten_o etc._n etc._n together_o with_o the_o variation_n of_o their_o figure_n and_o magnitude_n but_o the_o diameter_n of_o the_o body_n of_o the_o sun_n will_v be_v better_o take_v by_o the_o follow_a instrument_n and_o by_o reason_n that_o it_o will_v be_v often_o necessary_a to_o draw_v their_o figure_n more_o exact_o the_o engine_n that_o i_o have_v describe_v in_o my_o animadversion_n in_o the_o 67_o 68_o and_o 69_o page_n may_v be_v make_v use_n of_o to_o keep_v the_o helioscope_n always_o direct_v at_o the_o body_n of_o the_o sun_n which_o will_v be_v no_o small_a ease_n to_o a_o observer_n that_o be_v to_o delineate_v the_o figure_n on_o paper_n when_o the_o brightness_n and_o radiation_n of_o the_o moon_n venus_n or_o jupiter_n do_v somewhat_o offend_v the_o eye_n they_o will_v present_o lose_v their_o beard_n and_o look_v very_o distinct_a if_o one_o reflection_n from_o glass_n be_v make_v use_n of_o in_o the_o telescope_n another_o instrument_n i_o promise_v to_o describe_v be_v for_o take_v any_o such_o diameter_n transit_n or_o distance_n to_o the_o certainty_n of_o a_o second_o minute_n by_o which_o more_o may_v be_v do_v for_o the_o find_v the_o parallax_n of_o the_o superior_a planet_n and_o the_o longitude_n on_o the_o earth_n then_o have_v be_v ever_o yet_o do_v by_o all_o the_o instrument_n that_o have_v be_v use_v in_o the_o world_n 1._o this_o be_v make_v exact_o in_o all_o particular_n like_o the_o quadrant_n as_o to_o its_o hollow_a centre_n screwd-limb_n screw-frame_n and_o long_a rod_n to_o turn_v the_o screw_n from_o the_o centre_n and_o that_o the_o screw-frame_n may_v be_v keep_v down_o the_o true_a upon_o the_o edge_n of_o the_o limb_n there_o shall_v be_v make_v a_o small_a arm_n to_o clasp_v behind_o the_o inward_a limb_n of_o the_o instrument_n after_o the_o manner_n represent_v in_o the_o 8_o figure_n by_o w_n by_o which_o mean_v the_o screw_n will_v be_v keep_v close_o steady_a and_o even_o to_o the_o outward_a edge_n of_o the_o limb._n the_o letter_n in_o this_o 8_o figure_n be_v the_o same_o with_o those_o of_o the_o 1_o and_o 11_o figure_n of_o the_o animadversion_n and_o represent_v the_o same_o part_n need_v no_o further_o explanation_n 2._o instead_o of_o this_o screw_n upon_o a_o circular_a limb_n a_o screw_n 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r_o i_o say_v the_o superficies_n thereof_o shall_v be_v in_o the_o horizontal_n line_n o_o z_o for_o since_o the_o upper_a hemisphere_n be_v half_a the_o weight_n of_o the_o under_o the_o two_o quadrantal_a wedge_n p_o o_fw-fr h_n and_o h_n o_o r_o must_v necessary_o counterpoise_v the_o quadrantal_a wedge_n r_o o_fw-fr z_o of_o the_o oil_n three_o suppose_v that_o more_o than_o half_a the_o say_a oil_n or_o liquid_a pabulum_fw-la be_v consume_v and_o that_o there_o be_v only_o leave_v enough_o to_o fill_v the_o wedge_n b_o o_fw-fr z_o i_o say_v the_o counterpoise_v upper_a hemisphere_n now_o make_v the_o under_o and_o place_v in_o the_o position_n a_o h_n c_o r_o b_o o_o a_o shall_v exact_o counterpoise_v the_o say_a wedge_n of_o liquor_n so_o as_o that_o the_o superficies_n thereof_o shall_v be_v in_o the_o line_n o_o z_o for_o the_o wedge_n r_o o_fw-fr b_o of_o the_o aforesaid_a upper_a hemisphere_n do_v counterpoise_v the_o wedge_n c_o o_fw-fr r_o on_o the_o other_o side_n of_o 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diametrical_o opposite_a to_o this_o at_o c._n these_o two_o hole_n be_v the_o centre_n hole_n in_o which_o two_o small_a pin_n or_o centre_n fasten_v into_o two_o opposite_a point_n of_o the_o hoop_n or_o frame_n be_v make_v fit_a to_o move_v by_o which_o mean_v the_o say_a hoop_n be_v preserve_v in_o a_o horizontal_a position_n d_o d_o be_v this_o hoop_n or_o frame_n which_o be_v make_v to_o encompass_v the_o vessel_n or_o receptacle_n of_o the_o oil_n and_o be_v shape_v exact_o like_o it_o this_o be_v make_v strong_a enough_o of_o brass_n iron_n silver_n or_o other_o material_a to_o bear_v the_o receptacle_n poise_n and_o oil_n without_o bend_v and_o have_v as_o i_o say_v before_o two_o pin_n or_o gudgeon_n at_o c_o and_o opposite_a to_o it_o diametrical_o or_o semicircular_o upon_o which_o the_o say_a hoop_n always_o hang_v horizontal_o it_o have_v also_o on_o each_o side_n in_o the_o middle_n between_o the_o aforesaid_a pivot_n two_o centre_n as_o at_o f_o and_o e_o to_o receive_v 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full_a with_o oil_n or_o other_o liquor_n to_o the_o horizontal_n prick_v line_n l_o l_o which_o pass_v through_o the_o centre_n or_o axis_n of_o its_o cavity_n by_o the_o counterpoise_n move_v on_o the_o centre_n c._n h_o h_n h_n represent_v that_o counterpoise_n which_o be_v make_v exact_o half_a the_o weight_n of_o the_o oil_n or_o liquor_n and_o the_o centre_n of_o gravity_n of_o it_o must_v be_v somewhere_o in_o the_o line_n m_o m_o and_o it_o ought_v to_o be_v fit_v as_o exact_o into_o the_o hollow_a of_o the_o receptacle_n as_o it_o be_v possible_a that_o there_o may_v be_v leave_v as_o little_a space_n as_o may_v be_v between_o its_o convex_a side_n and_o the_o concave_a of_o the_o receptacle_n
but_o yet_o so_o much_o must_v be_v leave_v that_o it_o may_v move_v very_o free_o upon_o its_o centre_n c_o a_o whole_a semicircle_n this_o do_v and_o the_o receptacle_n be_v fill_v with_o oil_n the_o same_o effect_n will_v follow_v as_o in_o the_o first_o contrivance_n and_o the_o demonstration_n of_o it_o be_v much_o the_o same_o i_o shall_v not_o now_o spend_v time_n to_o explain_v it_o but_o rather_o proceed_v to_o the_o description_n of_o a_o three_o way_n of_o keep_v the_o liquor_n counterpoise_v to_o the_o same_o level_n the_o three_o way_n than_o be_v take_v any_o round_a vessel_n who_o concavity_n and_o convexity_n be_v turn_v upon_o a_o axis_n and_o suspend_v that_o vessel_n upon_o two_o small_a pivot_n but_o yet_o big_a enough_o to_o bear_v the_o say_a vessel_n fill_v with_o oil_n etc._n etc._n fasten_v in_o the_o pole_n of_o that_o axis_n and_o leave_v or_o cut_v open_a a_o six_o part_v more_o or_o less_o as_o you_o please_v of_o the_o side_n thereof_o that_o thereby_o 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axis_n who_o pole_n be_v in_o p_o the_o space_n between_o a_o and_o b_o in_o the_o side_n thereof_o be_v leave_v open_a into_o the_o cavity_n of_o it_o this_o vessel_n be_v suspend_v upon_o its_o pole_n at_o p_o so_o as_o to_o be_v free_a to_o move_v round_o upon_o they_o and_o exact_o poise_v as_o no_o one_o side_n thereof_o be_v heavy_a than_o another_o to_o the_o hollow_a of_o this_o vessel_n be_v fit_v a_o float_n d_o of_o brass_n latton_n silver_n lead_v etc._n etc._n who_o underside_n be_v make_v of_o a_o convexity_n just_o fit_a for_o the_o concavity_n of_o the_o vessel_n as_o may_v be_v see_v at_o k_o d_o i_o and_o the_o upper_a straight_o or_o plain_a let_v this_o float_n be_v make_v somewhat_o light_a than_o the_o oil_n or_o liquor_n on_o which_o it_o be_v to_o swim_v so_o that_o a_o part_n thereof_o may_v float_v above_o the_o superficies_n thereof_o let_v one_o end_n thereof_o e_o be_v fasten_v to_o the_o side_n of_o the_o vessel_n a_o little_a below_o the_o brim_n b_o 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must_v hang_v heavy_a on_o the_o brim_n b_o and_o consequent_o must_v move_v it_o down_o towards_o b_o till_o the_o upper_a side_n f_o g_o of_o the_o float_n be_v reduce_v to_o a_o parallelism_n with_o the_o superficies_n of_o the_o remain_a oil_n and_o the_o end_n e_o have_v no_o gravitation_n on_o the_o brim_n b_o which_o motion_n will_v be_v continue_v as_o the_o oil_n waste_v and_o the_o brim_n b_o will_v be_v move_v downward_o by_o the_o point_n b_o 1_n b_o 2_o b_o 3_o to_z b_o 4._o i_o shall_v not_o therefore_o spend_v any_o more_o time_n in_o the_o geometrical_a demonstration_n thereof_o but_o proceed_v to_o explain_v a_o four_o way_n by_o which_o the_o flame_n and_o superficies_n of_o the_o oil_n keep_v always_o at_o the_o distance_n they_o be_v first_o put_v at_o the_o four_o way_n than_o be_v the_o make_v the_o socket_n of_o the_o wick_n to_o swim_v upon_o the_o top_n of_o the_o oil_n so_o that_o the_o socket_n may_v sink_v as_o well_o as_o the_o oil_n by_o reason_n it_o be_v sustain_v by_o that_o and_o by_o that_o only_a the_o vessel_n or_o receptacle_n be_v general_o make_v of_o glass_n and_o it_o be_v best_o of_o a_o hemispherical_a figure_n the_o light_n cast_v itself_o through_o the_o body_n of_o the_o oil_n as_o well_o as_o of_o the_o glass_n this_o be_v so_o plain_a and_o obvious_a and_o so_o common_o use_v and_o practise_v that_o i_o need_v not_o spend_v more_o time_n in_o the_o explanation_n or_o demonstration_n thereof_o but_o proceed_v to_o describe_v a_o five_o way_n the_o five_o way_n than_o be_v much_o upon_o the_o same_o principle_n with_o the_o four_o but_o avoid_v several_a inconvenience_n to_o which_o that_o be_v subject_a for_o whereas_o the_o flame_n in_o the_o four_o be_v necessitate_v to_o be_v within_o the_o capacity_n or_o the_o receptacle_n in_o this_o five_o it_o may_v be_v at_o any_o distance_n and_o so_o be_v make_v much_o more_o convenient_a to_o be_v come_v at_o and_o to_o be_v dress_v and_o trim_v take_v then_o a_o vessel_n 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to_o return_v or_o bend_v upward_o again_o so_o that_o the_o plain_a of_o the_o upper_a superficies_n of_o the_o oil_n may_v cut_v that_o end_n of_o the_o siphon_n where_o the_o flame_n be_v between_o the_o top_n of_o the_o mouth_n of_o it_o next_o the_o socket_n and_o the_o return_n thereof_o upward_o then_o by_o a_o counterpoise_n so_o suspend_v this_o siphon_n that_o it_o may_v follow_v the_o oil_n as_o it_o waste_v and_o fit_a into_o the_o return_n of_o the_o siphon_n a_o socket_n and_o wick_n for_o the_o flame_n to_o be_v continue_v a_o contrivance_n somewhat_o of_o this_o kind_n you_o have_v in_o divers_a author_n and_o therefore_o i_o shall_v spend_v less_o time_n in_o the_o description_n thereof_o let_v a_o a_o a_o a_o in_o the_o six_o figure_n then_o represent_v a_o large_a cylindrical_a viol_n of_o glass_n through_o the_o mouth_n b_o of_o which_o the_o cavity_n thereof_o may_v be_v fill_v with_o oil_n and_o also_o the_o end_n d_o and_z float_n c_o of_o a_o convenient_a siphon_n may_v be_v put_v in_o this_o siphon_n d_o d_o d_o p_o g_o must_v be_v make_v long_o enough_o that_o the_o float_n c_o may_v reach_v the_o bottom_n of_o the_o vessel_n when_o the_o oil_n be_v spend_v and_o the_o other_o end_n thereof_o must_v be_v so_o curve_v that_o the_o knee_n of_o the_o siphon_n p_o may_v be_v below_o the_o superficies_n of_o the_o oil_n e_o f_o and_o yet_o that_o the_o socket_n h_n make_v for_o hold_v the_o wick_n for_o the_o flame_n i_o may_v be_v somewhat_o above_o it_o this_o siphon_n d_o d_o d_o p_o g_o with_o its_o socket_n and_o float_n shall_v be_v so_o counterpoise_v with_o a_o weight_n m_o hung_v over_o a_o pulley_n k_o by_o a_o string_n l_o that_o the_o float_n may_v not_o sink_v deep_a into_o the_o surface_n of_o the_o liquor_n but_o swim_v as_o it_o be_v at_o the_o top_n this_o do_v if_o the_o wick_n i_o be_v light_v the_o surface_n of_o the_o oil_n will_v be_v keep_v always_o at_o the_o same_o distance_n below_o the_o flame_n that_o it_o be_v first_o put_v at_o in_o the_o first_o three_o four_o and_o five_o way_n the_o flame_n of_o the_o lamp_n descend_v equal_a space_n with_o the_o superficies_n of_o the_o oil_n in_o the_o vessel_n and_o therefore_o though_o for_o some_o use_v it_o be_v very_o convenient_a as_o in_o annealing_n where_o thing_n be_v to_o be_v cool_v by_o degree_n yet_o for_o many_o other_o it_o be_v not_o especial_o in_o lamp_n furnace_n where_o the_o same_o heat_n be_v to_o be_v continue_v and_o in_o some_o case_n gradual_o increase_v for_o such_o case_n therefore_o the_o first_o and_o second_o way_n will_v be_v very_o convenient_a in_o some_o other_o case_n the_o six_o and_o seven_o way_n which_o do_v much_o the_o same_o thing_n the_o six_o way_n than_o be_v this_o through_o a_o arm_n or_o siphon_n like_o the_o branch_n of_o a_o lamp_n hang_v against_o a_o wall_n fix_v in_o any_o convenient_a place_n the_o oil_n from_o the_o receptacle_n be_v continual_o and_o equal_o supply_v to_o the_o flame_n of_o the_o lamp_n by_o the_o raise_n of_o the_o receptacle_n as_o fast_o as_o the_o oil_n waste_v so_o as_o to_o keep_v the_o superficies_n of_o the_o oil_n always_o in_o the_o same_o horizontal_n plain_n the_o receptacle_n be_v raise_v by_o a_o counterpoise_n hang_v upon_o a_o fusey_n which_o fusey_n be_v a_o part_n of_o a_o archimedean_a spiral_n let_v c_o c_o then_o in_o the_o seven_o figure_n represent_v the_o receptacle_n for_o the_o oil_n be_v a_o cylindrical_a or_o prismatical_a vessel_n of_o what_o bigness_n or_o length_n you_o please_v to_o this_o by_o two_o ear_n at_o l_o l_o fasten_v two_o line_n or_o rope_n k_o k_o the_o end_n of_o both_o which_o be_v fasten_v to_o the_o wheel_n or_o pulley_n g_z though_o one_o of_o they_o do_v run_v over_o the_o pulley_n f._n fit_a into_o this_o receptacle_n be_v make_v a_o cylindrical_a or_o prismatical_a plug_n a_o a_o which_o be_v fix_v in_o some_o convenient_a place_n so_o as_o not_o to_o rise_v or_o sink_v and_o through_o the_o middle_n thereof_o pass_v a_o siphon_n b_o b_o b_o the_o one_o end_n whereof_o extend_v like_o the_o branch_n of_o a_o candle_n or_o lamp_n sustain_v the_o socket_n d_o for_o the_o flame_n e_o which_o be_v feed_v with_o oil_n through_o the_o siphon_n b_o b_o b_o by_o the_o rise_a receptacle_n c_o c._n to_o the_o side_n of_o the_o pulley_n g_o be_v fasten_v a_o fusey_n h_n make_v with_o very_o great_a care_n of_o one_o revolution_n of_o a_o archimedean_a spiral_n not_o begin_v from_o the_o centre_n but_o from_o some_o convenient_a distance_n from_o it_o where_o the_o weight_n i_o hang_v may_v just_o counterpoise_v the_o receptacle_n c_o c_o when_o quite_o empty_a of_o oil_n the_o other_o hang_v counterpoise_n tangent_fw-la to_o the_o large_a part_n of_o this_o spiral_n must_v be_v so_o far_o distant_a from_o the_o centre_n of_o the_o wheel_n g_o that_o the_o same_o weight_n i_o may_v just_o counterpoise_v the_o say_a receptacle_n fill_v topful_a of_o oil_n and_o the_o fusey_n must_v be_v file_v true_a to_o a_o spiral_n draw_v with_o great_a care_n of_o one_o revolution_n between_o those_o two_o point_n i_o say_v here_o of_o one_o revolution_n because_o i_o have_v suppose_v the_o wheel_n or_o pulley_n g_o big_o enough_o by_o one_o revolution_n of_o it_o to_o draw_v up_o the_o receptacle_n the_o whole_a space_n it_o be_v to_o be_v raise_v for_o if_o the_o say_v pulley_n be_v so_o small_a as_o to_o require_v two_o three_o four_o or_o more_o revolution_n then_o must_v the_o piece_n of_o the_o spiral_n between_o those_o point_n be_v draw_v of_o two_o three_o four_o or_o more_o revolution_n proportionable_o which_o be_v very_o artificial_o and_o mechanical_o perform_v the_o receptacle_n c_o c_o will_n be_v raise_v by_o the_o same_o degree_n by_o which_o the_o oil_n be_v consume_v at_o e_o and_o the_o upper_a superficies_n thereof_o shall_v always_o be_v in_o the_o same_o horizontal_n line_n mm._n the_o geometrical_a and_o mechanical_a reason_n of_o which_o be_v so_o very_o plain_a i_o hope_v i_o shall_v not_o need_v to_o spend_v any_o more_o time_n in_o the_o explication_n thereof_o than_o only_o to_o say_v that_o by_o mean_n of_o the_o archimedean_a spiral-fusey_a the_o power_n of_o the_o weight_n i_o upon_o the_o pulley_n g_o decrease_v in_o the_o same_o proportion_n as_o the_o weight_n of_o the_o oil_n in_o the_o receptacle_n c_o c_o be_v diminish_v by_o its_o consumption_n the_o seven_o way_n than_o be_v by_o a_o cylindrical_a or_o prismatical_a plug_n fit_v into_o a_o cylindrical_a or_o prismatical_a receptacle_n and_o let_v down_o into_o it_o by_o a_o counterpoise_n hang_v upon_o a_o spiral_n fusey_n the_o oil_n be_v so_o raise_v in_o that_o receptacle_n as_o always_o to_o stand_v brimful_a or_o to_o the_o same_o horizontal_n height_n till_o the_o whole_a oil_n be_v consume_v the_o contrivance_n of_o this_o way_n will_v be_v very_o easy_o understand_v by_o any_o one_o that_o shall_v peruse_v the_o delineation_n in_o the_o eight_o figure_n and_o examine_v it_o by_o this_o follow_a description_n let_v a_o a_o in_o the_o eight_o figure_n then_o represent_v a_o cylindrical_a or_o prismatical_a receptacle_n stand_v fix_v upon_o a_o table_n or_o pedestal_n from_o the_o side_n of_o which_o issue_v a_o hollow_a arm_n or_o branch_n b_o b_o bear_v the_o socket_n for_o the_o wick_n c_o where_o the_o flame_n d_o be_v continue_v into_o the_o cavity_n of_o this_o receptacle_n be_v fit_v a_o cylindrical_a or_o prismatical_a plug_n e_o e_o big_a enough_o to_o fill_v the_o whole_a capacity_n thereof_o and_o yet_o not_o so_o close_o but_o that_o it_o may_v free_o slip_v up_o and_o down_o the_o cavity_n of_o the_o say_a receptacle_n without_o sink_v let_v this_o plug_n be_v make_v considerable_o heavy_a than_o the_o oil_n of_o the_o receptacle_n that_o be_v let_v the_o counterpoise_n l_o hang_v upon_o the_o little_a wheel_n m_o just_o reduce_v its_o gravity_n to_o be_v equal_a to_o that_o of_o the_o oil_n then_o let_v the_o point_n i_o where_o the_o perpendicular_a touch_v the_o spiral_n be_v so_o far_o remove_v from_o the_o centre_n of_o the_o wheel_n h_n that_o the_o counterpoise_n l_o may_v just_o take_v off_o its_o whole_a gravity_n and_o suffer_v it_o to_o have_v no_o degree_n of_o gravity_n or_o pressure_n downward_o then_o draw_v the_o spiral_n n_z o_o p_o according_a to_o the_o direction_n i_o give_v in_o the_o former_a way_n and_o the_o effect_n will_v be_v produce_v the_o geometrical_a and_o mechanical_a demonstration_n of_o which_o be_v very_o plain_a to_o any_o one_o that_o shall_v consider_v that_o as_o the_o plug_n e_o e_z by_o sink_v into_o the_o receptacle_n a_o a_o so_o far_o as_o to_o raise_v the_o oil_n to_o the_o horizontal_n superficies_n m_o